104.09 Lines, Grades, and Elevations
General
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To ensure uniformity and to reduce errors the procedures, methods and policies presented in this section should be followed.
A large portion of engineering costs is represented by construction staking. If errors occur in staking, the cost can be considerable to MDOT. The survey crew is to stake according to the standards stated at the end of each section and to build in independent checks to eliminate errors. For example: an operation involving a level should never be terminated without checking into a known elevation; alignment operations, such as bridge layout or sewer staking, are not to be left before checking into known control points.
Construction survey notes generated by hand are to be recorded in bound field books. If data has been developed by computer, three-ring binders are acceptable. Data generated with data collectors and total stations or GPS units must be downloaded and a hard copy provided. It must be provided in a format that can be checked for accuracy and content by manual computations. Field books/binders should be identified on the cover with control section number, job number, subject (alignment, slope stake, bench marks, etc.) and each book numbered for cross-referencing. The Engineer's name, address and phone number are to be placed on the first page in case the book is misplaced. An index must be placed in the front of each field book. Pages are to be numbered.
Computations, such as grade sheets and bridge underclearances, are to be included. All notes are to be neat, clean, legible, complete and information is to be clear so another crew can continue the work or make computation checks.
The date, weather, crew, instrument type and crew chief’s signature are to be listed with each day's notes. Errors should have a line drawn through them, or the word "void" printed across a page, and a note referring to the location where the correct notes are to be found. Erasures are not to be used.
All computations and field notes are to be included in the files at the end of the project and are a matter of record. MDOT reserves the right to check anytime. Various examples of field notes are included throughout this section.
MDOT will determine how the project is to be staked depending upon staff availability. All consultant and Contractor staking projects require quality assurance checks at the frequency shown under Consultant/Contractor Quality Assurance Guidelines later in this section. Responsibilities and standards for specific types of staking operations are listed with the discussion of these activities.
Topographic Symbols
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The topographic symbols shown here are to be used for all survey drawings and notes. Additional symbols are available from Design.
Checking Plans
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Plans must be checked for errors and omissions of detailed information needed for the layout.
- Horizontal alignment needs to be checked. Bearings with delta angles, curve data, spiral data, coordinates with bearings and distances need to be verified. Care should be taken to distinguish construction centerline, which is the basis for proposed work, from survey centerline which is established to depict the existing roadway. Legal centerline, if used, should be distinguished from either design or survey centerline. Assistance in interpretation can be obtained from Design Surveys and the Real Estate Support Area. If coordinates have not been included on the plans, they are generally available from the design unit (except bridges). If they are not available, they can be generated through Simplicity software, or other similar packages (if you need help contact the Construction and Technology Field Engineering Unit). Before using IGRDS-generated coordinates with Simplicity software, Y and X need to be substituted for North and East (Y is always North/South and X is always East/West).
- The vertical alignment must be computed from PVI to PVI and to the connection at each end to ensure proper grade percentages are used. Plan typicals are to be checked before completing grade sheets. Superelevation lengths transition and location should be checked to be sure the proper standard plan has been used. Curb and gutter and gore grades should be checked to ensure proper fit along roadway for positive drainage. Grades for projects generated through the computer need to be checked. Contact the Construction and Technology Field Engineering Unit for assistance.
- Sewer and utility grades are to be computed for possible conflicts with each other and conflicts with ditches, pavement and bridges. Catch basins should be checked to be sure they are at the low points. Some field work may have to be done to avoid conflicts.
- Bridges need to be checked for proper alignment with the roadways and for proper clearance. Be sure to check for proper orientation of structure units when staking bridges. All dimensions of footings, piers, caps, rockers, beams and decks must be checked before staking. Reference points and lines for bridge work should be established and witnessed before any work begins at the site. Pile driving data is available though the Construction and Technology Field Engineering Unit. Profile grades at the road and bridge connections need to be checked, as well as the cross section and the bulkhead elevations. Deck grades also will need to be checked after obtaining the actual beam elevations. (See Division 7 of this manual for more on structure elevations.)
- ROW plans need to be checked for proper ties needed for layout, adequate room for construction, utility conflicts and potential sight distance problems. Coordinates are frequently not given unless the ROW is to be monumented. However, the various computer programs used for design can usually generate coordinates close enough for construction layout (construction is to pull any fence 1.0 foot inside of the actual line). Descriptions, ROW plans and old data is available through the Real Estate Support Area.
Preliminary Staking
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Before work can begin, project control must be established. MDOT or their representative is responsible for establishing horizontal control, ROW, vertical control and bridge stakeouts unless covered by a special contract. Cross sections are to be taken by the Contractor on Contractor staking projects but still must be monitored by MDOT. On projects without Contractor staking, MDOT will take all cross sections. If plan quantity for earthwork is agreed upon, only enough cross sections to verify the design sections are required.
Horizontal Controls
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Horizontal control begins with locating the control points, traverse points, mapping points, section corners, etc., set by Design surveys. These points will be noted on the plans along with respective witnesses. From these, all PC, PI, PT, TS, SC, PIS, CS, ST and POT points are established. Supplying these points is not necessary if coordinate points are given and correlation between the end points is established. If points are not found, they must be established by traversing, or the use of coordinates with total stations or GPS units. Contact the Construction and Technology Support Area, Field Engineering Unit for assistance with traversing or coordinate work.
From these control points, the horizontal alignment, conforming to the centerline shown on the plans, is established. Deflection angles at PIs and tangent distances, or long chord distances, must be checked and recorded. Distances between control points on the tangent should not exceed 1000 feet and should be closer on rolling terrain. Coordinate points may be established by MDOT instead of PC, PI, PT, etc., if agreed upon by the Contractor and the Engineer and provided that MDOT has checked alignments, etc. and has provided notes to the Contractor to tie these together.
All control points should be either witnessed or backed up by traverse points outside the construction influence area, unless GPS or total station with roadway staking software or radial staking will be used during the life of the contract. When possible, witness alignment points outside the construction limits. Consideration must be given to future use of the control points. Vertical difference between final position of the control point and its witnesses must be considered along with location of control points offset for construction staking. When deflections occur in the ROW, establishing control points and witnesses at these locations is advised.
One method of witnessing alignment points is by measuring a minimum of three bearings and distances to permanent and prominent objects as shown in Figure 104-1. Generally, reference caps will be attached to these objects. Witnesses should be less than 100 feet away. Avoid small acute angles between witnesses, and witnesses 180° from one another.
Applications: Used on resurfacing projects, etc., where witnesses will remain undisturbed and an offset line will not be needed.
A second method of witnessing alignment points is by establishing the angle and distance to tacked hubs set at convenient distances. The hubs should be set where they will not be disturbed during construction and are accessible enough for a transit, or total station to be set over them. (Figure 104-2).
Applications: Often used when witnessing PIs. If the interior angle is bisected, the midpoint can easily be established.
A third method is similar to the second but has two sets of witnesses (tacked hubs) at known angles and distances from the centerline. Having the two lines approximately 90° from one another is desirable. (Figure 104-3)
Applications: Frequently used for control points that fall within an intersection. A very accurate method, because two transits, or total stations, can be used thereby eliminating chaining.
A fourth method again uses tacked hubs, but the witnesses are set 90o to the construction centerline (Figure 104-4). This allows the survey crew to establish any offset lines with minimal transit setups. This is probably the most desirable method.
Applications: Commonly used on widening and relocation projects where offset lines will be run parallel to the construction centerline. When POCs on long curves are to be witnessed, this method should be used. To witness a POC at right angles to the curve, the transit or total station is set on the point. After taking a backsight, the deflection angle for the transit station is turned and 90o is added or subtracted to the vernier, depending on which way the witnesses are to be established.
A fifth method can now be used since total stations have become so accurate and coordinates are readily available. This method establishes an independent baseline with coordinates tied in with the centerline points. Then, when centerline, or offset points, are to be established, they can be done radially. This method saves time witnessing but requires more time on the computer generating offset coordinates, (Figure 104-5).
Applications: Saves much of the witnessing time, particularly when many witnesses will not be preserved. Once the control points have been set, the baseline points are established anywhere that they will be safe (preferably on high ground with good visibility). Then, angles and distances
from a control point to the baseline points are measured. The baseline points can now be tied to the centerline coordinate system by traversing. Contact the Construction and Technology Field Engineering Unit for assistance. Simplicity software works very well. When GPS is used, witnessing will not be necessary. However, traverse points may be needed if future construction operations will not be using GPS.
Horizontal Control Responsibilities
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MDOT Staking Projects:
- MDOT will establish POB, POE, POT, PI, PC, PT, TS, PIS, SC, CS and ST for each alignment and run line when needed. Points are to be no more than 1000 feet apart and visible from adjacent points.
Consultant Staking for MDOT (project control):
- Consultant will set all the above-mentioned control points and run line as needed.
- MDOT will make random QA field checks, at the frequency required and record findings.
- MDOT will make random computation checks of alignment notes and record findings.
- Alignment notes are to be made available on request and become part of the project records upon completion of the project.
Contractor Staking Projects:
- MDOT will set the control points as previously noted.
- Contractor will witness and preserve the control points and then run line as needed to construct the project.
- MDOT will make random QA field checks as required and record findings.
- MDOT will make random computation checks of alignment notes and record findings.
When a consultant monitors for MDOT:
- MDOT will check consultant documentation to assure the QA checks have been made as required and record findings.
- MDOT will make random field checks, of the same points the consultant checked, as needed and record findings. Alignment notes are to be made available on request and become part of the project records upon completion of the project.
Design Build Projects:
- Details are to be spelled out in the scope of the project. When no detailed information is given, the responsibilities will revert back to the standard specifications and current special provisions.
Horizontal Control Standards
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All distances are to be measured and recorded to the nearest 0.01 foot.
When setting control points, angles need to be turned and recorded to the nearest 5 seconds.
When setting witness points, angles need to be turned and recorded to the nearest 10 seconds, unless method 5 is used. Then angles need to be turned to the nearest 5 seconds.
Horizontal Curves
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Before running horizontal curves or spirals, the data should be checked and deflection angles and chord lengths computed. If coordinates are going to be used, they can be generated by various software packages and then staked radially (checks must be made to assure all points are on the curve). Stakeout can also be performed with data collectors using their road packages. Highway curves are generally done by arc definition and railroad curves by chord definition (some older road projects were done using chord definition). Projects using English units of measure are usually keyed on the degree of curve. With metric curves, the key becomes the radius (no longer use D), (Figure 104-6.)
Terminology and formulas used in horizontal curve computations are shown below.
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Δ = External Angle (Delta). |
Will be provided by Design. |
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R = Radius |
Will be provided by Design. |
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T = Length of Tangent |
R Tan Δ/2. |
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LC = Long Chord |
2 R sin Δ/2. |
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E = External Distance |
T Tan Δ/4. |
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M = Middle Ordinate Distance |
R(1-cos Δ/2). |
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L = Length of Curve |
100 Δ/D, or 100ΔR/5729.578 |
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PC = Point of Curvature |
Stationing = PI Station - T. |
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PI = Point of Intersection |
Will be provided by Design. |
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POC = Point on Curve |
PC + Arc Length |
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POCT = Point of Curve Tangent |
Back Tangent : PC + Tangent Distance Forward Tangent : Represented with the PI Station + Tangent Distance |
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PT = Point of Tangent |
Stationing = PC station + L. |
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MP = Midpoint of Curve |
Stationing = PC station + L/2. |
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Deflection Angle per foot |
360°F 4R TT (English curves) or D/200 |
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Any Chord Length |
2R(Sin Deflection Angle). |
Another common curve parameter is the degree of curve (D) which defines the sharpness of the curve in terms of the radius.
For highways, degree of curve is defined as the central angle subtended by 100 feet of arc and is calculated in terms of the radius as :
R = 5729.578/D or D = 5729.578/R
For railroads, degree of curve is defined as the central angle subtended by 100 feet of chord and is calculated in terms of the radius as :
R = 50 sin D/2
EXAMPLE PROBLEM NO. 1 - HORIZONTAL CURVE
Given:
Δ = 87° 00' 00" Rt (87.0 decimal degrees)
R = 1000 feet
PI = Sta. 11+17.48
Staking interval of 50 feet
Offset of 22 feet to inside of curve
Compute:
Curve Parameters, Deflection Angles, Short Chords, Offset Chords
D = 5729.578 / 1000 = 5° 43' 46.5"
T = 1000 x tan (87°) / 2 = 948.96 feet
LC = 2 x 1000 x sin (27°) / 2 = 1,376.71 feet
E = 948.96 x tan (87°) / 4 = 378.60 feet
M = 1000 (1 - cos 87° /2) = 274.63 feet
L = (100 x 87°) / 5° 43' 46.5" = 1,518.44
PC = (11 + 17.48) - 948.96 = Sta 1 + 68.52
MP = (9 + 072.779) + 455.531/2 = Sta 9 + 27.74
PT = (9 + 072.799) + 455.531 = Sta 16 + 86.96
Compute Deflection Angles
Deflection Angle = distance x deflection angle per foot
Deflection angle per foot = D / 200 (convert D to decimals of degrees first) 0.028648
(Note: when computing by hand, do not round this value too soon)
Deflection angle from PC to the MP, PT and to each 50 foot stake are tabulated here.
| Dist.(ft) | Defl. Angle per Foot | Decimal Degrees | Defl. Angle | |
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| From PC to Sta 2+00 | 31.48 | 0.028648 | 0.90187 | 0° 54' 06.6" |
| Between any 50 foot stakes | 50.00 | 0.028648 | 1.43245 | 1° 25' 56.6" |
| From Sta 9+00 to MP (9+27.74) | 27.74 | 0.028648 | 0.79472 | 0° 47' 40.9" |
| From MP to Sta 9+27.74 to 9+50 | 22.26 | 0.028648 | 0.63773 | 0° 38' 15.7" |
| From Sta 16+50 to PT (16+86.96) | 36.96 | 0.028648 | 1.05887 | 1° 03' 31.8" |
The deflection angles are tabulated in Figure 104-7 along with the cumulative total deflection angles. The total deflection angle should equal Δ/2 providing a good check. (Rounding of decimals of seconds may result in a slight difference).
If a curve is being computed by hand, this is a convenient method because it provides a check on your math computations. See Figure 104-7 for sample field notes.
Software packages such as Sight Survey by Simplicity Systems do a good job with this type of computation. They will also generate a chord from the PC to each station which is a method for staking a curve using the total station.
Compute short chords
Short Cord = 2R (sine of the deflection angle)
From PC to Sta 2 + 00.00 2(1000) (sin 0deg 54' 06.7") = 31.48 feet
Between any two 50 foot stakes 2(1000) (sin 1deg 25' 56.6") = 50.00 feet
From Sta 9 + 00.00 to MP 2(1000) (sin 0deg 47' 41") = 27.74 feet
From MP to Sta 9 + 50.00 2(1000) (sin 0deg 38' 15.6") = 22.26 feet
From Sta 16 + 50.00 to PT 2(1000) (sin 1deg 03' 31.9") = 36.96 feet
Compute offset chords using the following ratios
New Radius/ Original Radius = New Chord/ Original Chord
For an offset of 22 feet to the inside of the actual curve the new Radius is 78 feet
1000 - 22 / 1000 = New Chord / 31.48 or 30.79 feet
1000 - 22 / 1000 = New Chord / 50.00 or 48.90 feet
1000 - 22 / 1000 = New Chord / 27.74 or 27.13 feet
1000 - 22 / 1000 = New Chord / 22.26 or 21.77 feet
1000 - 22 / 1000 = New Chord / 36.96 or 36.15 feet
Chords can also be computed radiating from the PC. This procedure requires only two people for the field work. Deflection angles remain the same but new chords must be computed using the total deflection angles tabulated on the next page. For this example the following centerline chord can be computed from the PC to the MP.
Chord = 2 R (sine of the total deflection angle)
Chord = 2(1000) (sin 21° 45' 01.2") = 741.12
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*Error due to Rounding of Factor and Stationing
Alignment Books
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When bound books are used, they are generally set up so that the control points and witnesses are shown for a curve, followed by the curve data.
Computer Printouts
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When computer generated data is used, the printouts should be placed in a three-ring binder. A bound book showing witnesses will still be needed.
Figure 104-8 shows a typical format for a Sight Survey Simplicity Systems example.
When running horizontal curves, it is often necessary to set up somewhere on the curve, or on the PT. The procedure used for running a curve while setting anywhere on the curve other than the PC is as follows:
- Set the angle on the vernier for the point being sighted. Plunge the telescope and turn the angle for the next station; if setting on the PT, or backing the curve in, do not plunge - just turn directly.
Coordinate Method
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With data collectors, total stations, and GPS units, curves and offsets can also be staked out from remote locations by use of coordinates generated from various software packages; or from data collectors using internal software routines.
Spirals
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Spirals are being used frequently on new alignment projects. Standard Plan R-107 explains when spirals are to be used. When spirals are used, the spiral leading into the curve and the spiral leaving the curve will normally be the same (Figure 104-9). Table XII must be used to compute the spiral parameters. Deflection angle and chord data are computed using the formulas shown on the following pages.
Terminology used in spiral computations is shown below. Many of these parameters are computed as shown in example problem #2 using factors from spiral tables given later in this section.
Figures 104-10 through 104-12 show examples of spiral curve field notes.
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TS Tangent to spiral |
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SC Spiral to curve. |
Stationing = TS Station + Length of Spiral |
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CS Curve to spiral. |
Stationing = SC Station + Length of Curve. |
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ST Spiral to tangent. |
Stationing = CS Station + Length of Spiral. |
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PIS Point of Intersection for the spiral. |
Stationing = TS Station + Long Tangent or Stationing = ST Station - Long Tangent |
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PICC Point of Intersection for the Curve. |
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PI Point of Intersection before adding spirals. |
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Ls Length of spiral. |
200ΔsR/5729.578 (English). |
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P Amount of Shift for the Curve. |
(Use spiral tables) |
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K Distance from the relocated PC to TS. |
(Use spiral tables) |
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LT Long Tangent for the spiral. |
(Use spiral tables) |
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ST Short Tangent for the spiral. |
(Use spiral tables) |
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Δs Spiral External Angle. |
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Δc Curve External Angle. |
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Δ External Angle before adding spirals. |
(Δs + Δc + Δs) or (2Δs + Δc). |
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X Distances along the Long Tangent from the TS or ST to a point opposite the SC or CS. |
(Use spiral tables) |
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Y Offsets from Long Tangent to the spiral TS or ST. |
(Use spiral tables) |
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LCs Long Chord for the spiral. |
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Ts Distances from TS or ST to Original PI. |
(R + P) (tanΔ/2) + k. |
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Spiral Deflection Angle |
[(sta. dist/Ls)2]/3 x Δs |
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Short Chords |
Difference in deflection angles, times 3, multiplied by a factor from the spiral tables. |
Given:
Δ = 110° 25' 30"Rt.
Δs = 15° 16' 44"
R = 300 feet
TS = 34 + 65.72
Staking interval of 25 feet
Compute:
Curve Parameters, Deflection Angles, Short Chords using factors from spiral tables.
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Δc = |
(110° 25' 30") - 2(15° 16' 44") = 79° 52' 02". |
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Ls = |
[200 (15° 16' 44") R] / 5729.578 = 160.00 feet. |
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P = |
0.02216 x 160.00 = 3.55 feet. (0.02216 is found in Table XII under °/Da) |
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K = |
0.49881 x 160.00 = 79.81 feet. (0.49881 is found in Table XII under Xo/Da) |
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LT = |
0.66917 x 160.00 = 107.07 feet. (0.66917 is found in Table XII under LT) |
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ST = |
0.33561 x 160.00 = 53.70 feet. (0.33561 is found in Table XII under ST) |
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X = |
0.99291 x 160.00 = 158.87 feet. (0.99291 is found in Table XII under X) |
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Y = |
0.08844 x 160.00 = 14.15 feet. (0.08844 is found in Table XII under Y) |
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LCs = |
0.99684 x 160.00 = 159.49 feet. (0.99684 is found in Table XII under LC) |
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Ts = |
(300 + 3.55) tan 110° 25' 30"/2 + 79.81 = 516.76. |
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PIs = |
(in spiral) = (34 + 65.72) + 107.07 = 35 + 72.79 |
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SC = |
(34 + 65.72) + 160.00 = 36 + 25.72. |
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CS = |
(36 + 25.72) + length of curve or (length of curve = 100 Δ/D = 418.18) Therefore, the CS = (36 + 25.72) + 418.18 = 40 + 43.90 |
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ST = |
(40 + 43.90) + 160.00 = 42 + 03.90. |
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PIS = |
(out spiral) = (42 + 03.90) - 107.07 = 40 + 96.83. |
Compute deflection angles - because a spiral is an arc with a continually changing radius, each defection angle must be computed starting from the tangent points, TS or ST, using the equation:
Deflection Angle = [(Dist / Ls)2 / 3] x (Δs)
From TS to Sta 34 + 75.00 is 9.28 feet.
[(9.28 / 160)2 / 3] x (15°16'44") = 00°01'01.2"
From TS to Sta 3.5 + 00.00 is 34.28
[(34.28 / 160)2 / 3] x (15°16'44") = 00°14'01.6"
Each deflection angle is calculated in this manner.
Compute short chords - The short chord lengths are also continually changing and are computed from point to point as follows.
- Compute the difference in deflection angles (in decimal degrees) from TS or ST to station and multiply by 3.
- Compute the distance from TS or ST to station.
- Go to spiral table for Δ° and read LC Factor.
- Multiply distance by the LC Factor from spiral table.
3 times the difference in deflection angles TS to Sta 34+75.00=0.05
The distance is 9.28 feet
In Table XII for Δ° = 0.05 the LC Factor is 1.0000
Therefore the short chord = 9.28 (1.0000) = 9.28 feet
Between any two stakes 3 times the difference in deflection angles to compute Δ.
Difference, in stations, from 34 + 75.00 to 35 + 00.00 = 0.21678 x 3 = 0.65
In Table XII for Δ° = 0.65 the LC Factor is 0.999995
Therefore the short chord = 25.000 (0.999995) = 24.9999 or 25.00 feet
The chords can also be computed radiating from the TS to any station.
3 times the difference in deflection angle TS to 35 + 00.00 = (0.0° 14' 01.6" - 0° 00' 00") / (0° 14' 01.6" x 3) = 0.7
The distance is 34.28
In Table XII for Δ° = 0.7 the LC Factor is 0.99999
Therefore, the short chord is 34.28 (0.99999) = 34.28 feet
The previous example is the way to compute spiral data by hand. Sight Survey will also compute spirals. However, it will not do offsets. The computer programs will vary from the hand computed version due to approximations in the tables.
See Figure 104-13 for sample printout for this example generated using Sight Survey by Simplicity Systems.
Note: This program generates data from the TS to the midpoint of the curve; then starts at the ST and works back to the midpoint of the curve.
The data below works only when setting on the TS for In Spiral and on the ST for the Out Spiral. If it becomes necessary to set up anywhere else, new deflection angles and chords must be computed. These computations require a different set of formulas. If this needs to be done, contact the Construction and Technology Field Engineering Unit.
Another thing unique to a spiral is that the deflection angles from the PIS to the TS to the SC is always equal to Δs/3. The angle formed by PIS and SC to TS is 2 Δs/3. (Figure 104-14).
Use of Tables XII & XIII - Spiral Tables - General Explanation
D Degree of central circular curve (Da = arc definition of D; Dc = chord definition of D).
Ls Length of spiral curve.
Δ Central angle of the spiral, or spiral angle.
X, Y Coordinates (abscissa and ordinate) of the SC referred to the TS as origin and to the initial tangent as X-axis.
Xo, Yo Coordinates (abscissa and ordinate) of the offset TC, which is the point where a tangent to the circular curve produced backward becomes parallel to the tangent at the TS.
LT Long tangent of the spiral.
ST Short tangent of the spiral.
LC Long chord of the spiral.
EXAMPLE PROBLEM for USE of SPIRAL CURVE TABLES
when solving for P & K
For arc definition
Ls = 200 feet and Δs = 9 30 >
P = 0.01381 x 200 = 2.76 '
K = 0.49954 x 200 = 99.91 >
For chord definition
Ls = 200 feet and Δs = 9 30 >
P = (0.01381-0.0010) x 200 = 2.56 >
K = (0.49954-0.0120) x 200 = 97.508 >
* Multiply functions (except * values) by the given value of Ls. When chord definition of degree of curve (Dc) is used, correct the calculated values of o or Xo by subtracting the product of Dc and the * values.
* Multiply functions (except * values) by the given value of Ls. When chord definition of degree of curve (Dc) is used, correct the calculated values of o or Xo by subtracting the product of Dc and the * values.
* Multiply functions (except * values) by the given value of Ls. When chord definition of degree of curve (Dc) is used, correct the calculated values of o or Xo by subtracting the product of Dc and the * values.
* Multiply functions (except * values) by the given value of Ls. When chord definition of degree of curve (Dc) is used, correct the calculated values of o or Xo by subtracting the product of Dc and the * values.
* Multiply functions (except * values) by the given value of Ls. When chord definition of degree of curve (Dc) is used, correct the calculated values of o or Xo by subtracting the product of Dc and the * values.
* Multiply functions (except * values) by the given value of Ls. When chord definition of degree of curve (Dc) is used, correct the calculated values of o or Xo by subtracting the product of Dc and the * values.
- Multiply functions (except * values) by the given value of Ls. When chord definition of degree of curve (Dc) is used, correct the calculated values of o or Xo by subtracting the product of Dc and the * values.
* Multiply functions (except * values) by the given value of Ls. When chord definition of degree of curve (Dc) is used, correct the calculated values of o or Xo by subtracting the product of Dc and the * values.
* Multiply functions (except * values) by the given value of Ls. When chord definition of degree of curve (Dc) is used, correct the calculated values of o or Xo by subtracting the product of Dc and the * values.
Right-of-Way
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ROW limits should be established before construction begins. Stakes marking the ROW line should be set on both sides of the construction centerline at 100 foot intervals (50 foot intervals should be used on sharp curves), including all corners marking a change in width or direction. A 1 inch x 4 inch x 36 inch stake marked with “ROW” is used to designate ROW limits. The plans may call for the ROW line to be fenced. When fencing is required, the fence will be placed 1 foot inside the ROW limits. Accuracy is extremely important. ROW plans, along with description of each parcel, are available through the TSC office or Lansing Real Estate Support Area. ROW monumentation will be set by Design Survey Section, region surveyor, or by contract.
Preservation of Land and U.S. Survey Monuments
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During construction, extreme care must be taken to preserve all section and quarter corner monuments. When construction operations require the obliteration of an existing monument, it is to be witnessed and replaced as soon as the construction operations have progressed to where it will not be disturbed. This work shall be performed under direct supervision of a professional surveyor licensed in the State of Michigan. If a corner can be reestablished in its original location without disturbing the existing witnesses, no further action needs to be taken. However, if any witnesses are disturbed and have to be replaced, or if the existing corner is significantly changed, the changes will have to be recorded.
Monument boxes are to be placed over all section corners where the existing monument falls in a hard surfaced highway. Even though a monument box is placed, witnessing the monument is still necessary. When a section or quarter corner is not in a public highway, the monument will be set not more than six inches above the surface of the surrounding ground, nor more than six inches below the surface. When a corner occurs in a public highway that is not hard surfaced, the monument is to be placed at least six inches below the surface as stated in Act 74 of 1970 as amended by Act No. 313 P.A. of 1975:
The Contractor is responsible for preserving, witnessing and reestablishing section corners and quarter corners. This work is to be done as soon as possible and must be performed by a registered land surveyor. See Figure 104-15 for divisions of a section.
Policy Regarding Geodetic Markers
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All geodetic bench marks, GPS monuments and triangulation points found on a construction project should be preserved. When any of these markers are located within construction limits, the area supervising land surveyor should be notified immediately. Triangulation points require a high order survey to relocate, and the services of the National Geodetic Surveyor (NGS) are usually secured to do the work. The area supervising land surveyor will institute the action necessary in this case. Bench marks are often reset by MDOT. Again, the area supervising land surveyor is notified so that proper forms and a new bronze marker can be secured from the Construction Field Engineering Unit.
Applicable Excerpts from Surveying Acts
(Refer to Design Survey Manual for more complete citations). -Reserved-
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- (a) “Property corner” means a geographic point on the surface of the earth, which is on, is a part of, and controls a property line.
- (b) “Property controlling corner” for a property means a public land survey corner or any property corner which does not lie on a property line of the property in questions but which controls the location of 1 or more of the property corners of the property in question.
- (c) “Public land survey corner” means any corner actually established and monumented in an original survey or resurvey used as a basis of legal description for issuing a patent for the land to a private person from the United States government.
- (d) “Corner” unless otherwise qualified, means a property corner, a property controlling corner, a public land survey corner or any combination of these.
- (e) “Accessory to a corner” means any exclusively identifiable physical object whose spatial relationship to the corner is recorded. Accessories may be bearing trees, bearing objects, monuments, reference monuments, line trees, pits, mounds, charcoal-filled bottles, steel or wooden stakes or other objects.
- (f) “Monument” means an accessory that is presumed to occupy the exact position of a corner.
- (g) “Reference monument” means a special monument that does not occupy the same geographical position as the corner itself but whose spatial relationship to the corner is recorded and which serves to witness the corner."
- (h) “Licensed surveyor” means a surveyor who is licensed to practice land surveying under the occupational code, Act No. 299 of the Public Acts of 1980, being sections 339.101 to 339.2721 of the Michigan Compiled Laws, and has a paid-up license for the calendar year, or who is authorized under that act to practice land surveying.
- (i) “Board” means the board of land surveyors, as established by section 2002 of the occupational code, Act No. 299 of the Public Acts of 1980, being section 339.2002 of the Michigan Compiled Laws.
- History: 1970, Act. 74, Imd. Eff. July 16, 1970; Am. 1975, Act 313, Eff. Mar. 31, 1976; Am 1988, Act 26, Eff. May 1, 1988.
- Sec. 3. A surveyor shall complete, sign, stamp with his seal and file with the register of deeds of the county where the corner is situated, a written record of corner establishment or restoration to be known as a "corner record" for every public land survey corner and accessory to such corner that is established, reestablished, monumented, remonumented, restored, rehabilitated, perpetuated, or used as control in any survey by such surveyor, and within 90-days thereafter, unless the corner and its accessories are substantially as described in an existing corner record filed in accordance with the provisions of this act.
- Sec. 7. In every case where a corner record of a public land survey corner is required to be filed under the provisions of this act, the surveyor shall reconstruct or rehabilitate the monument of such corner and accessories to such corner, so that it shall be left by him in such physical condition that it remains as permanent a monument as is reasonably possible and so that the same may be reasonably expected to be located with facility at all times in the future.
- History: 1970, Act 74, Imd. Eff. July 16, 1970.
- Sec. 8. A corner record shall not be filed unless it is signed by a licensed surveyor and stamped with the surveyor’s seal, or in the case of an agency of the United States government or the state, the certificate may be signed by the chief of the survey party making the survey, and approved, signed and sealed by the licensed surveyor in responsible charge of the agency.
- History: 1970, Act 74, Imd. Eff. July 16, 1970; Am 1988, Act 26, Eff. May 1, 1988.
- Sec. 10. When a monument is set and it is not in a public highway, the monument shall be set not more than 6 inches above the surface of the surrounding ground nor more than 6 inches below the surface of the ground. When a corner occurs in a public highway which is not hard-surfaced, the monument shall be placed at least 6 inches below the surface of such highway. When a highway is hard-surfaced at the corner, whether by concrete, tarvia, or otherwise, a circular opening at least 6 inches in diameter shall be left at the corner and properly covered with a metal cover. The monument shall be placed in the opening beneath the cover.
- History: Add. 1975, Act 313, Eff. Mar. 31, 1976.
- Sec. 14. (1) A person who defaces, destroys, alters, or removes a corner is guilty of a misdemeanor and shall be punished by a fine of not more than $500.00, or imprisonment for not more than 60 days, or both, and shall be responsible for the costs or reestablishment, replacement, and filing of the corner by a licensed land surveyor. A corner may be temporarily removed for construction purposes if the corner is properly witnessed by a licensed land surveyor prior to removal. The corner shall be reset, re-witnessed, and re-filed by a licensed land surveyor within 30days after the completion of construction. A corner shall not be temporarily removed for more than 1 year. A person who knows that a corner has been defaced, destroyed, altered, or removed shall report that fact to the county surveyor of the county in which the corner is located.
- (2) As used in this section, "person" means an individual, or any public or private legal entity.
- History: Add. 1975, Act 313, Eff. Mar. 31, 1976; Am. 1988, Act 26, Eff. May 1, 1988.
Divisions of a One Mile Section
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ROW Staking Responsibilities
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Staking Projects:
MDOT will establish ROW for all projects (those requiring fence and those not requiring fence). Stakes will be set every 100 feet on tangent sections and every 50 feet on curves when necessary. Stakes will also be set anytime there is a deflection in the ROW line. ROW easements will also need to be staked.
Consultant Staking Projects:
Consultant will stake ROW as outlined above.
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random checks for compliance with ROW plans and record findings.
Any computations or field notes are to be made available on request and become part of the project records upon completion of the project.
Contractor Staking Projects:
Contractor is to preserve the ROW stakes and to stay inside the ROW. When it becomes necessary to remove section corners, they are to be witnessed, reset and recorded (by a registered land surveyor, licensed in the State of Michigan) as soon as construction activities will no longer disturb them.
Design/Build Projects:
Details are to be spelled out in the scope of the project. When no detailed information is given, the project responsibilities will revert to the standard specifications and current special provisions.
ROW Staking Standards
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All distances are to measured and recorded to nearest 0.01 feet.
All angles are to be turned to the nearest 5 seconds or better.
After setting the ROW line, any fencing is to be pulled inside 1.00 feet.
Any time the project calls for ROW Monumentation, or Monumentation Preservation, the work must be done by a registered land surveyor, licensed in the State of Michigan.
Vertical Control
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Before any level work is done on a project, the bench marks shown on the plans must be checked for elevation and location. It is the policy of the department to use National Geodetic Surveys (NGS) datum when possible. A complete record of all known NGS bench marks is maintained in the Lansing design office. Municipal surveys shall be on the datum used by the municipality and must be compared with the datum used by MDOT.
Bench marks should be established at locations that will be convenient for future work. It is also convenient to alternate on left and right side of the roadway, particularly when work is to be done under traffic. Good bench marks are placed on permanent or semipermanent objects. Examples are a stamped brass disk, spike and nut in exposed tree roots; a steel post driven in the ground; or a chiseled A+@ in foundation walls, headwalls or on the top of fire hydrants. Bench mark number and elevations are to be painted on the bench or guard stake.
Locating Bench Marks
- At each end of large structures.
- At points of change from cut to fill.
- At high and low points.
- Locations that are handy for cross sectioning of side hills.
- Any time there is a difference of 25 feet in elevation in rolling terrain.
Bench Loops
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In order to verify or establish elevation for bench marks, they must be looped with a minimum of three bench marks in the loop. Readings are to be recorded to the nearest 0.01 foot and the loop must check within 0.01 foot when checking into any bench mark. Before starting a bench loop operation the level must be checked. Check level vials and make a two peg test. The tapes and shoes on the rods along with the tripod head & shoes also need to be checked.
Several methods of looping bench marks are used. Examples of field notes for each method are shown. Level books are usually set up with descriptions and elevations in the front and loop notes and computations in the back.
One method of looping bench marks is to use a single rod system as shown in Figure 104-16. For convenience and accuracy, distance between the instrument and the rod should not exceed 250 feet and should be balanced within each setup.
Another method for looping between bench marks is the three-wire method. This requires the operator to record all three cross hair readings, total the readings, divide by three then compare the average with the middle reading (should be within 0.01 foot) before moving the instrument. This method seems slower but will generally catch wrong readings and eliminate the need to redo the loop. Distances between the instrument and the rod should not exceed 250 feet and distances from instrument to the rod need to be balanced. (Figure 104-17).
A third method is to use a laser level. The instrument needs to be checked out before starting. Lasers are generally tight enough for construction staking, but may not be tight enough for bench looping. They are normally used to check the difference between two benches, but not for looping because the instrument may be off in an X or Y direction, or the band may be too wide. When lasers are used for looping, two readings need to be taken and averaged. To take the readings, come from the top down until reading is stable and then come up from the bottom until the reading is stable. (Figure 104-18)
A fourth method, and the one which is probably the most accurate, is to use the digital level and let the instrument take the readings. Readings can be recorded as in the single rod method or can be recorded internally and dumped to a computer when completed. The computer can process the data, adjust the net, if proper software is loaded, and print out the bench mark elevations. Instruments can be set to average readings and to display to 0.001 foot.
Bench loops can also be done with total stations depending upon the vertical angle accuracy. When this method is used, the prism needs to be read with the scope in the direct and in the inverted positions. Both readings are recorded and then averaged. Care must be taken when sighting the prism - a target on the prism is recommended. When processing the notes be mindful of algebraic signs (you always add BS and subtract FS but the way you handle the readings vary. This method is not generally used for looping, but is used to transfer a bench to the top or bottom of a hill. (Figure 104-19)
Vertical Control Responsibilities
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MDOT Staking Projects:
MDOT will establish bench marks approximately every 1000 feet along the project. MDOT will also set at least two near each bridge site. These will be looped and an elevation established for each one. The bench mark elevations and looping notes will be in a bound book, or on an electronic printout. This data will be supplied to the Contractor.
Consultant Staking for MDOT (project control):
Consultant will set the bench marks at the frequency noted above.
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random computation checks of bench loop closures and record findings.
Bench mark notes will be made available on request and become part of the project records upon completion of the project.
Contractor Staking Projects:
MDOT will set bench marks at the frequency noted above.
Contractor will preserve or move the bench marks to safe locations. If others are needed, the Contractor will be responsible for establishing locations and determining the elevations. Any new bench marks, elevations and looping notes will be supplied to MDOT.
Contractor is expected to check into each bench mark (every 1000 feet ).
MDOT will make random QA field checks, at the required frequency, of any new bench loops and will record findings.
When a consultant monitors for MDOT (Consultant CE projects):
MDOT will check consultant documentation to assure the QA checks have been made and record findings.
MDOT will make random field checks as needed and record findings.
Bench mark notes are to be made available on request and become part of the project records upon completion of the project.
Design/Build Projects:
Details are to be spelled out in the scope of the project. When no detailed information is given, the project responsibilities will revert to the standard specifications and current special provisions.
Vertical Control Standards
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Checks for bench mark to loops must be within 0.01 foot. When checking into a bench mark after grading stakes, the tolerance is 0.03 foot.
Vertical Curves
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MDOT generally uses equal tangent vertical curves. An equal tangent vertical curve sketch is shown in Figure 104-20.
Terminology and formulas used in vertical curve computations are shown below.
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See Plans | |
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See Plans | |
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Half the horizontal distance between the PVC and the PVT. | |
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Computed horizontally along stations. | |
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Distance from Curve to PVI | |
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Distance from PVC to any station up to the PVI and then figured from the PVT back toward the PVI. | |
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Offset from curve to tangent (t2 / T2) x E. | |
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High or Low point (G1 x L) / (G1 - G2) = distance from PVC | |
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Point of vertical curve (curve starts). | |
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Point of vertical intersection. | |
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Point of vertical tangent (curve ends). |
EXAMPLE PROBLEM NO. 3 - VERTICAL CURVE:
Given: L = 400 feet Find: Vertical Curve Parameters
G1 = +2.56% Tangent Elevations
G2 = - 1.84% Offsets
PVI (Station) = 36 + 82.58 Curve Elevations
PVI elevation = 744.03 High Point of Curve
Calculate the vertical curve parameters
E = [(G2 - G1) / 8] x L/100 = [(-1.84 - 2.56) / 8] x (400/100) = -2.20
Tangent elevations are calculated using the elevations of the PVC or PVT and subtangent distances and grades.
PVC 34 + 82.58 = 738.91
35+ 00 = 739.36
35 + 50 = 740.64
36 + 00 = 741.92
36 + 50 = 743.20
PVI 36 + 82.58 = 744.03
37 + 00 = 743.71
37 + 50 = 742.79
38 + 00 = 741.87
38 + 50 = 740.95
PVT 38 + 82.58 = 740.35
Offsets are computed from the PVC or PVT.
Y = (t2 / T2) x E (computed from the PVC)
34 + 82.58 = 0.000
35 + 00 becomes: (17.422 2002) x -2.20 = -0.02
35 + 50 becomes: (67.422 2002) x -2.20 = -0.25
36 + 00 becomes: (117.422 2002) x -2.20 = -0.76
36 + 50 becomes: (167.422 2002) x -2.20 = -1.54
36+ 82.58 becomes: (2002 2002) x -2.20 = -2.20
Y = (t2 / T2) x E (computed from the PVT)
37 + 00 becomes: (182.582 2002) x -2.20 = -1.83
37 + 50 becomes: (132.582 2002) x -2.20 = -0.87
38 + 00 becomes: (82.582 2002) x -2.20 = -0.38
38 + 50 becomes: (32.582 2002) x -2.20 = -0.06
38 + 82.58 = 0.000
Curve Elevations are computed from the tangent elevations and offsets.
34 + 82.58 = 738.91 - 0.00 = 738.91
35 + 00 = 739.36 - 0.02 = 738.34
35 + 50 = 740.64 - 0.25 = 740.39
36 + 00 = 741.92 - 0.76 = 741.16
36 + 50 = 743.20 - 1.54 = 741.66
36 + 82.58 = 744.03 - 2.20 = 741.83
37 + 00 = 743.71 - 1.83 = 741.88
37 + 50 = 742.79 - 0.97 = 741.82
38 + 00 = 741.87 - 0.38 = 741.49
38 + 50 = 740.95 - 0.06 = 740.89
38 + 82.58 = 740.35 - 0.00 = 740.35
High Point
HP = (G1 x L) / (G1 - G2)
HP = (2.560 x 400) (2.560 - (-)1.840 = 232.73
HP = 232.73 feet from the PVC or at station 37 + 15.31
Tangent elevation at 37 + 15.31 = 743.43
Offset elevation at 37 + 15.31 = -1.54
Curve elevation at the HP = 741.89
The same procedure is used for finding the low point of a vertical curve where the back tangent is a minus grade and the front tangent is a plus grade.
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36 + 82.580 34 + 82.580 35 + 00.000 35 + 50.000 36 + 00.000 36 + 50.000 37 + 00.000 37 + 15.307 37 + 50.000 38 + 00.000 38 + 50.000 38 + 82.580 36 + 82.580 (PVI) |
744.030 P.I. 738.910 P.C. 739.339 740.386 741.158 741.654 741.876 741.889 HIGH POINT 741.823 741.494 740.891 740.350 (P.T.) 741.830 |
Cross Sections
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The purpose of cross sectioning is to determine accurate information from which to compute earthwork quantities. Before starting, the crew chief should instruct the members of the level party on the method to be used and the purpose for cross sectioning. Cross sections will be taken every 50 feet along centerline and at sufficient intermediate stations to provide a true representation of the ground surface.
Original Cross Sections
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Cross sections may be taken with some form of level, total station, GPS unit or from aerials. Cross section notes are a permanent record and will be kept in a bound level book or in an electronic file. If an electronic file is used, a hard copy must be provided also or a disk. Cross sections will be needed for original ground, undercuts, muck holes, etc. and for the final section. (Figure 104-23)
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Taken at right angles to the construction centerline or baseline. |
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Taken right and left of construction centerline with zero distance reading on the centerline and readings progressing outward. |
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Taken at least every 25 feet outward from centerline and more often when needed. |
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Extend outward to the ROW line or beyond. In the case of a grading permit, cross sections should extend to include limits of permit. |
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Readings on ground surfaces are taken to the nearest 0.1 foot. |
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Readings on hard surfaces, such as pavement, curb, or railroad tracks are taken to the nearest 0.01 foot. |
Cross sections may be taken radially with a total station, GPS unit and data collectors, but end area plots will still be required for computing earthwork volumes. The Average End Area Method will generally be used to compute earthwork volumes and to provide a check on the slopes (final section). Even when staked section method, station grading, or Contractor staking is used, enough original and final sections are needed to verify the situation a minimum of every 500 feet. If the field checks suggest changes have occurred, the entire job will need to be sectioned.
In the case of ordinary ramps or circular ramps where minimal excavation is involved, it is more practical to use some sort of prismoidal correction. This is generally done by adjusting the distance between end areas based on the center of the end area. In the case of computer computations, this correction can be made by using the computer end areas and adjusting the distances between sections in the field.
Cross sections or depth measurements (when used in lieu of cross sections) of topsoil should be recorded and placed in the file. This data will be needed to determine quantities for earth excavation and embankment.
Taking cross sections throughout the project may be required for topsoil removal, subgrade undercutting, shallow muck areas, etc. Sometimes other means may be used, such as depth checks, hand level shots from preset grade stakes, etc. When surcharges are used, they will need to be cross sectioned. The sections should extend down the sides of the charge to original ground.
The Contractor is required to furnish a boat to help in obtaining the sections in shallow muck holes or borrow areas under water. Attempting to get sections with a man suspended in a drag line bucket is dangerous and not allowed. When the area cannot be sectioned using a boat, borings may be required.
Borrow/Wetland Sections
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In the occasional instance where it is necessary to measure borrow or wetland site volume, it is to be measured in the same manner as roadway excavation. If the site is adjacent to the road under construction, the regular road cross sections can be extended to include the area involved. Sections should be taken at such intervals necessary to establish the ground profile (generally every 25 feet along the baseline and every 25 feet or less, perpendicular to the baseline).
If the borrow or wetland site is separate from the construction area, the limits must be clearly staked as a guide to the Contractor. ROW stakes, with the legend “borrow limits,” are to be placed around the perimeter of the borrow site after first verifying the limits of excavation. An entire quarter section may be indicated on the permit, when the owner simply intended a knob or hill to be removed. Because of a condition in the agreement, grade stakes may be necessary to limit the depth of the excavation. In most cases, the borrow should be taken to a location best suited for drainage and appearance. Borrow areas shall be properly drained, unless otherwise provided as in wetland situations.
When borrow or wetland area cross sections are needed, baselines should be staked and witnessed to establish a reference for necessary sections. The witnesses should fall outside of any possible operation of the Contractor, and end points should be set so they can easily be extended if necessary. Cross sections are generally taken on a 25 feet grid and at intermediate pluses as necessary. Readings will be taken to the nearest 0.1 foot. If possible, the road datum should be used. If this is not practical, at least two bench marks are to be established outside the construction operations and referenced to an assumed datum.
A sketch of the borrow location should be shown on the first page of the notes. The sketch should include fences, baseline location and stationing, witnesses, bench marks, buildings or landmarks, and borrow limits. Also, include a description giving section, township, range, north arrow and any other information that will help those unfamiliar with the project to reestablish and carry on the work.
In most new borrow sites the topsoil overburden must be removed before suitable borrow can be obtained. In these instances, the site will need to be sectioned before and after topsoil removal unless the topsoil depth is uniform and the deduction from the borrow quantity can be accurately determined.
Original Cross Section Responsibilities
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Staking Projects:
MDOT will take original sections - enough to verify existing sections. If check sections indicate a problem, or if plan quantity is not agreed to, the entire project will need to be sectioned.
Consultant Staking for MDOT (project staking):
Consultant will take the sections as noted above.
MDOT will take random QA field checks at the frequency required and compare to design plots and record findings.
Cross section notes, plots and computations are to be made available on request and become part of the project records upon completion of the project.
Contractor Staking Projects:
MDOT will take sections (one per 500 feet) to verify design sections.
Contractor will take sections for entire project, if plan quantity has not been agreed to, and make plots along with earthwork computations by the average end area method.
MDOT will take random QA field checks at the frequency required and record findings.
MDOT will make random checks of the plotted sections and earthwork computations and record the findings.
When a consultant monitors for MDOT:
MDOT will check consultant documentation to assure the QA checks have been made and record findings.
MDOT will make random field checks as needed and record findings.
Cross section notes, plots and computations are to be made available on request and become part of the project records upon completion of the project.
Design/Build Projects:
Details are to be spelled out in the scope of the project. When no detailed information is given, the project responsibilities will revert to the standard specifications and current special provisions.
Original Cross Section Standards
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Taken every 50 feet along centerline when taken for quantity determination. Taken every 500 feet along centerline in open areas and every 50 feet in wooded areas when used to verify.
Maximum distance between shots is not to exceed 25 feet (left and right) and is recorded to the nearest 0.1 foot when readings are taken on the ground and 0.01 foot when taking readings on hard surfaces.
Borrow areas, or wetland replacement sites, are to be sectioned at 25 feet along centerline and at least every 25 feet left and right. If data is taken radially (with data collectors), software must be capable of generating plots every 25 feet. No matter how sections are taken, cross section plots are required.
Elevation readings are taken to the nearest 0.10 foot on ground surfaces and to nearest 0.01 foot on hard surfaces.
Intermediate & Final Cross Section Responsibilities
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MDOT Staking Projects:
MDOT will take all cross sections, make all necessary plots and compute end areas and volumes.
When plan quantity has been agreed to, final sections need to be taken every 500 feet to verify slopes.
Consultant Staking Projects:
Consultant will take all sections, make plots and compute end areas and volumes as noted.
MDOT will take random QA sections as required and record findings.MDOT will also make random QA checks on plots, end areas, volume computations and record findings.
Cross section notes, plots and computations are to be available on request and become part of the project records upon completion of the project.
Contractor Staking Projects:
Contractor will take all cross sections, make plots and compute end areas and volumes.
MDOT will take random QA sections at the frequency required and record findings.
MDOT will make random checks on plots, end area; volume computations and then record findings.
When a consultant monitors for MDOT:
MDOT will check consultant documentation to assure the QA checks have been and record findings.
MDOT will make random field checks as needed and record findings.
Cross section notes, plots and computations are to be made available on request and become part of the project records upon completion of the project.
Design/Build Projects:
Details are to be spelled out in the scope of the project. When no detailed information is given, the project responsibilities will revert to the standard specifications and current special provisions.
Intermediate & Final Cross Section Standards
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Take a maximum of every 50 feet plus odd locations along centerline when needed to determine limits or breaks.
Maximum distance between shots perpendicular to the baseline is not to exceed 25 feet and will be recorded to the nearest 0.1 foot.
When data is taken radially (with data collectors), software must be capable of generating plots at any interval not to exceed 50 feet.
Cross section plots will be required.
Readings will be taken to the nearest 0.1 foot.
CONSTRUCTION STAKING
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All construction staking and information given to the Contractor shall be properly documented. The crew chief or Engineer shall advise the Contractor and grade inspector of all information contained on the stakes. However, it is the Contractor's responsibility to understand all information on the stakes.
Each day's notes must include the date, weather conditions and members of the crew. Replacement of stakes, due to the careless operation of the Contractor, should be recorded in the notes showing time and crew members used in replacement of the stakes.
The following staking is required for construction. Each type of staking operation is discussed in this section.
Refer to Figure 104-24 for a roadway sketch and terminology used in this section.
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Clearing and grubbing stakes. |
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Slope stakes. |
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Subgrade stakes. |
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Pavement stakes. |
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Drainage stakes. |
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Utility stakes. |
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Tunnel stakes. |
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Sewer stakes. |
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Structure stakes. |
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Miscellaneous stakes. |
Clearing Stakes
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After the existing alignment has been re-established and the proposed alignment set and witnessed, the areas to be cleared are staked. Care must be taken to ensure adequate distance behind the slope stake for the vertical curve as required. An effort should be made to save trees when possible, while still meeting safety requirements. Sight distances must be taken into account, particularly at intersections. This will ensure a roadway that is both safe and pleasing to the motorist.
The stakes are set at right angles to the roadway centerline using a cloth tape. Measurements must be taken every 50 feet along centerline and at breaks. The stakes are marked "clear" or "C&G." Caution must be used to stay within the ROW limits. Field notes should show stationing, distance left and right, date and names of persons doing the staking. Sufficient information must be shown in the notes so that an accurate determination of clearing quantities can be made.
If slope stake data is not available, distances can be obtained from the computation output sheet for the preliminary earthwork computations or the original cross-section plots. These are available from the Design Support Area.
When individual tree or stump removal is required, the notes must be set up to indicate the station, distance left or right, and size. The date and names of individuals making measurements must also be documented. (Figure 104-26)
Clearing Staking Responsibilities
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Staking Projects:
MDOT will take measurements, set stakes every 50 feet and make sketches along with area computations.
Consultant Staking for MDOT (project staking):
Consultant will take all measurements and set stakes every 50 feet. They will also make all sketches and area computations.
MDOT will make random QA field checks at the frequency required. They will also make random QA checks on the computations and record findings.
Field notes and computations are to be made available on request and become part of the project records upon completion of the project.
Contractor Staking Projects (project staking):
Contractor will take all measurements, set stakes, make area computations and document with sketch and dimensions.
MDOT will make random QA checks on field measurements as required and a thorough check on computations used to determine pay item quantities and record findings.
When a Consultant Monitors for MDOT:
MDOT will check consultant documentation to assure the QA checks have been made and record findings.
MDOT will make random field checks as needed and record findings.
Field notes and computations are to be made available on request and become part of the project records upon completion of the project.
Design/Build Projects:
Details are to be spelled out in the scope of the project. When no detailed information is given, the responsibilities revert to the standard specifications and current special provisions.
Selective Thinning and Individual Tree/Stump Removal:
All locations, stakes and measurements will be taken by MDOT.
MDOT will also make plots and do the computations for determining pay quantity.
Clearing Staking Standards
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Clearing distances will be measured to the nearest 1 foot.
Tree and stump diameters will be measured to the nearest inch at a point 4.5 feet above the base of the tree.
W/2
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Before any slope staking can be performed, the distance from the centerline to the subgrade shoulder point must be computed. This distance is commonly referred to as W/2.
- Y - Vertical distance between the finished shoulder point and a point on the subgrade directly below the finished shoulder point.
- X - Horizontal distance between the finished shoulder point and the subgrade shoulder point.
The methods most commonly used to compute the subgrade shoulder point when there is no super elevation is illustrated in the following examples. Refer to Figure 104-27.
EXAMPLE PROBLEM NO. 4 - W/2 NO SUPERELEVATION
Given:
Y = (2.44) - (0.64) = 1.80
Subgrade slope = 2% or 0.02
Front slope = 1 on 6 or 0.1667
Other distances and elevations as shown in Figure 104-27
Compute the distance X
- X = Rate of front slope (Y) +/- [Rate of front slope [subgrade slope (X)]]
- X = 6 (1.80) + [6(0.02) (X)]
Note: use front slope rate not decimal
- X = 10.8 + 0.120 X
- X - 0.120 X = 10.8
- X = 10.8/0.88
- X = 12.27 feet
Distance (W/2) from centerline to the subgrade shoulder point is
- 12.0 + 10.0 + 12.27 = 34.27 feet from centerline.
The drop becomes:
- 12.27 x 0.02 = -0.25 or -0.25 + -2.44 = -2.69 feet from Plan Grade.
The distance X can also be computed by adding, (or subtracting, depending on whether the front slope is a cut or fill) the subgrade slope to the front slope (in decimal form) and dividing the result into the vertical distance Y.
- X = Y/(front slope - subgrade slope)
- X = 1.8/(0.1667 - 0.02)
- X = 1.8/0.14667
- X = 12.27
The total distance (W/2) from centerline to subgrade shoulder point is
- 12.0 + 10.0 + 12.27 = 34.27 feet.
A sketch for a superelevation section is shown in Figure 104-28 and example problem #5 illustrates the calculations.
EXAMPLE PROBLEM NO. 5 - W/2 WITH SUPERELEVATION
Given:
Subgrade slope = 6% or 0.06
Front slope = 1 on 4 or 0.25
Y = 2.00
X = 4(2.00) - 4(0.06X)
X = 8.00 - 0.24X
1.24X= 8.00
X = 6.45 feet from finish shoulder point to subgrade shoulder point
or
X = 2.00/(0.25 + 0.06) =2.00/0.31
X = 6.45 feet
Once the subgrade shoulder distances have been computed, the W/2 distances can be determined. The W/2 is merely a point of reference from which slope stakes are established.
In a section without ditches, W/2 is measured to the subgrade shoulder point. In a section with ditches, W/2 is normally measured to the point of intersection of the ditch bottom and the back slope. (Figure 104-29).
Occasionally, a swamp ditch is encountered. This is a ditch outside of the toe of slope and is independent. It will usually have its own W/2 and will be staked separately.
Slope Stakes
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Slope stakes are set at the intersection of proposed front slope with original ground in fill sections and at the intersection of back slope with original ground in ditch sections. See Figure 104-29 for slope stake locations. They mark the limits of excavations and embankments. Stakes should be set left and right of centerline every 50 feet. The slope stake should be set to the nearest 0.1 foot for distance and the ground elevations read to the nearest 0.1 foot.
Information is to appear on slope stakes for various types of grading sections, as shown in Figure 104-30. The stations are marked on the back, along with the W/2. On the front is the distance to centerline or reference line, ditch cut, cut or fill, ditch type and size, along with front and back slope ratios. Place stationing on the front side if space allows.
The reference point to which the cut or fill on the slope stake refers is generally the intersection of the subgrade and the fore slope. Some-times, the sand subbase and the fore slope intersection are used, or the finish shoulder point may be used. Whatever is used needs to be discussed with the Contractor. The purpose of the slope stake is to allow the grade checker to build the correct elevations and slopes from the slope stake back to the subgrade shoulder point. Situations may dictate a variable back slope to stay inside ROW, or to give a pleasing appearance. Modifying back slopes is generally easier and does not have a significant impact on safety standards. Normal slopes will be 1 on 2, 1 on 4, 1 on 6, etc.
Sometimes offsetting slope stakes from the true location is necessary; the offset shown on the stake is the distance from the offset location to the true location. The cut or fill shall be shown in reference to the ground at the location of the stake as set.
Figure 104-31 shows an example of slope stake and cross section field notes. The slope stake information is shown on the left page and the cross section data on the right. Another acceptable format is to use the right page for both cross sections and slope stake information.
Slope Staking Responsibilities
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MDOT Staking Projects:
MDOT will develop all grades and dimensions.
MDOT will set slope stakes every 50 feet.
Stakes will indicate cut or fill, slopes, ditch information and distance from centerline.
Consultant Staking for MDOT (project staking):
Consultant will compute all grades, including ditches, and present to the MDOT Engineer prior to staking.
Consultant will set slope stakes every 50 feet, or agreed upon interval (with MDOT Engineer).
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random computation checks of grades, distances, transitions and W/2s, then record findings.
Field books and grade computations are to be made available on request and become part of the project records upon completion of the project.
Contractor Staking Projects:
Contractor will make all grade computations and present to the MDOT Engineer prior to staking.
Contractor will set slope stakes every 50 feet, or agreed upon interval (with the MDOT Engineer).
MDOT will take random QA field checks as required and record findings.
MDOT will make random computation checks of grades, distances, transitions and W/2s, then record findings (notes become part of the record.).
When a Consultant monitors for MDOT:
MDOT will check consultant documentation to assure the QA checks have been made and record findings.
MDOT will make random field checks as needed and record findings.
Field books are to be made available on request and become part of the project records upon completion of the project.
Design/Build Projects:
Details will be spelled out in the scope of the project. When no detailed information is given, the project responsibilities will revert to the standard specifications and current special provisions.
Slope Staking Standards
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Distances will be measured to the nearest 0.1 foot.
Ground elevations for slope stake computations will be read to the nearest 0.1 foot.
Subgrade Stakes
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Subgrade stakes are set for use in trimming and finishing subgrade after rough grade operations have been completed from the slope stakes. They are generally set at 50 foot intervals. However, they may be set at 100 foot intervals depending upon Contractor's operation/equipment and whether the desired results can be achieved. In order to ensure proper drainage, the low points should be staked. All grade break points, as shown on the typicals, must be staked. The stakes may be offset at a distance agreed to with the Contractor. The grade shown on the stake should be set in reference to the top of the subgrade to the nearest 0.1 foot, marked by an arrow or crow's foot indicating which way the grade needs to go. Median ditch grades are often marked on the back side for expressway projects. (Figure 104-32).
Subgrade Staking Responsibilities
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MDOT Staking Projects:
MDOT will develop all grades and dimensions.
MDOT will set grade stakes every 50 feet.
Shoulder points and all break points will be staked.
Stakes will indicate the cut/fill and the amount of offset.
Consultant Staking for MDOT (project staking):
Consultant will compute all grades and present to MDOT Engineer prior to staking.
Consultant will set grade stakes every 50 feet.
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random computation checks of grades, distances, drainage and transitions, then record findings.
Field books and grade computations are to be made available on request and become part of the project records upon completion of the project.
Contractor Staking Projects:
Contractor will make all computations and present to the MDOT Engineer prior to staking.
Contractor will set grade stakes every 50 feet.
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random computation checks of grades, distances, drainage and transitions, then record findings (Field books become part of the project records).
When a Consultant Monitors for MDOT:
MDOT will check consultant documentation to assure the QA checks have been made and record findings.
MDOT will make random field checks as needed and record findings.
Field books and grade computations are to be made available on request and become part of the project records upon completion of the project.
Design/Build Projects:
Details will be spelled out in the scope of the project. When no detailed information is given, the project responsibilities will revert to the standard specifications and current special provisions.
Subgrade Staking Standards
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Distances will be measured to the nearest 0.1 foot.
Grade elevations will be staked to the nearest 0.1 foot.
Pavement Stakes
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Pavement stakes are set at intervals as shown below.
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Distance to the center of the structure. |
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Size, type of structure and type of cover. |
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Cut to the flow lines of the pipes inletting or outletting the structure. |
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Cut or fill to the top of masonry. |
These stakes are to be used for fine grading of sand subbase and aggregate base course and pavement. When stakes are left undisturbed, they can also be used for paving operations. After sand subbase and aggregate base course have been placed, the grades on the stakes need to be checked and a tack line placed; the tack line is required to provide proper alignment for the paving operation.
The pavement stakes will be placed at an offset distance agreed to by the Contractor. The grades will be referenced to the edge of the pavement. Two methods are being used to mark the grade on the stake. The first method, referred to as the extended grade method, is to grade the stake as though the pavement extended to the stake. The second method, referred to here as the pavement grade method, is to grade the stake with the edge of the pavement grade.
When using the extended grade method for pavement that drains all one way, a string will pass through the edge of pavement elevation when strung from the stake on one side to the stake on the other side. (Figure 104-33)
When the second method is used for pavements that drain all one way, a string grade will be required to allow the technician to check the grade. This method is commonly used when the Contractor is using a level to set forms from the stake. (Figure 104-34).
When the extended grade method is used for pavements with a crown, the string line will pass through each edge of pavement (Figure 104-35). Vertical distance from the string line to the pavement must be computed in order to check grade. (Figures 104-36)
While setting pavement stakes, the survey crew must check into bench marks within 0.01 foot and should do so every time one is near (approximately every two setups). When it becomes necessary to adjust the pavement grades due to level errors or grade corrections, this should be done gradually. When connecting new or reconstructed pavement with an existing pavement or structure, grades should be checked before grading the last setup. Figure 104-37 shows sample pavement grade field notes for both the Lenker and Frisco Rod setups.
Pavement Staking Responsibilities
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MDOT Staking Projects:
MDOT will develop all grades and dimensions.
MDOT will set grade stakes every 50 feet, or every 25 feet when curve radius is less than 1150 feet.
Stakes will indicate the cut/fill and amount of offset.
Consultant Staking for MDOT (project staking):
Consultant will compute all grades and present to the MDOT Engineer prior to staking.
Consultant will set stakes every 50 feet, or every 25 feet if the radius is less than 1150 feet.
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random QA checks on grade computations and record findings.
Field books and grade computations are to be made available on request and become part of the project records upon completion of the project.
Contractor Staking Projects:
Contractor will compute all grades and present to the MDOT Engineer prior to staking.
Contractor will set stakes every 50 feet, or every 25 feet if the radius is less than 1150 feet.
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random QA checks on grade computations and record findings.
When a Consultant Monitors for MDOT:
MDOT will check consultant documentation to assure the QA checks have been made and record findings.
MDOT will make random field checks as needed and record findings.
Field books and grade computations are to be made available on request and become part of the project records upon completion of the project.
Design/Build Projects:
Details will be spelled out in the scope of the project. When no detailed information is given, the project responsibilities will revert to the standard specifications and current special provisions.
Pavement Staking Standards
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Stakes are to be measured to the nearest 0.01 foot.
Grade elevations will be staked to the nearest 0.01 foot.
Culvert Stakes
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Stakes will be set for all culverts. Staking is most conveniently done after the drainage ditches are defined. Stakes will be placed at an offset distance, agreed to by the Contractor, from the ends of the culvert on short pipes, or parallel to its centerline on long pipe runs. (Figures 104-38 and 104-39). On the longer runs, stakes should be set every 50 feet. The stakes should show the cut/fill to flow line on the front side. The offset distance from end of culvert, size and the class of pipe should be shown on the back side.
Culvert plan lengths should be checked according to the formula in the current standard plans and staked to the nearest commercial length which takes into account the minimum safety requirements. Caution must be used when computing metal culverts to account for staked lengths and pay lengths. Before computations can be made, you must know whether the culvert will be metal or concrete, and whether end sections or headwalls are called for, so that the proper standard is used. If the proposed culvert is unsafe per the plans, the designer should be notified. Designers should show pay length quantities to the nearest commercial length of pipe.
Figures 104-40 a, b and c show examples of culvert staking field notes.
Culverts are occasionally on a skew angle (Figure 104-41). When this occurs, the culvert is first computed as though it were at a 90-degree angle to centerline. The skew angle is then accounted for. The following example illustrates the calculations.
EXAMPLE PROBLEM NO. 6 -SKEW CULVERT LENGTHS
Given:
Skew angle of 70° to centerline
Assumed 90° lengths of 65.40 feet right and 61.25 feet left
Compute:
Actual lengths at 70° using the triangular relationship
Cosine = adjacent/hypotenuse
Right side computation
Cos 20° = 65.40 feet/actual length
Actual length = 65.40 feet/0.93969 = 69.60 feet
Left side computation
Cos 20° = 61.25 feet/actual length
Actual length = 61.25 feet /0.93969 = 65.18 feet
Total culvert length is 69.60 + 65.18 = 134.78 feet
Now the commercial length, safety requirements and the staked length required must be taken into account to determine the total number of feet needed at this location.
Drainage Stakes
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Stakes for location and grade for sewer lines, curb and gutter and drainage structures will be set for the Contractor to build the project and for inspection forces to check progress.
Structures will be located by placing a stake at the center of the structure as shown in Figure 104-42. Two or more tacked reference stakes will be set at an offset agreed to by the Contractor. These stakes will be offset from the center of the structure and will show the following information.
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Flow line grades and top of masonry grades will be on the front side of the stake. The offset and information for sewer lines and structures will be placed on the back side.
The Contractor should be advised how close to the top of the masonry the stake is graded, because the final adjustment is usually done when the final grade for the paving, or curb and gutter, are set (inlet flow lines to catch basin covers are staked slightly lower than the gutter grade to ensure drainage). Location, cuts, fills, crew data and sketch showing the stakeout will be placed in the field book. (Figure 104-43).
Sewer lines will be staked at an offset distance from the centerline of the sewer, as agreed to by the Contractor. The stakes will have the flow line grade on the front side and the size and type of sewer, along with the trench detail, on the back side. When lasers are not used for laying pipe, stakes will be set at 50 foot intervals or less. When lasers are used, stakes will be set at the intervals directed by the Engineer to allow inspection operations to randomly check for grade or alignment deviation.
Curb and gutter grade stakes will be set at 50 foot intervals or less. They will be staked to the nearest 0.01 foot. The top of the curb grade will be shown on the front side of the stake, and the type of curb and gutter, along with the offset, on the back side. The line of stakes are set parallel to the back of the curb at an offset agreed to by the Contractor. (Figure 104-44).
Drainage Staking Responsibilities
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MDOT Staking Projects:
MDOT will develop all grades and dimensions.
MDOT will place grade stakes every 50 feet or less and at agreed upon offset.
Stakes will indicate cut/fill to flow lines and top of the masonry grade, plus amount of offset.
Consultant Staking for MDOT (project staking):
Consultant will compute all grades and present to the MDOT Engineer prior to staking.
Consultant will set stakes as noted under MDOT staking.
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random QA checks on grade computations and locations and record findings.
Field books and grade computations are to be made available on request and become part of the project records upon completion of the project.
Contractor Staking Projects:
Contractor will compute all grades and present to the MDOT Engineer prior to staking.
Contractor will set stakes every 50 feet or less and at agreed upon offset.
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random QA checks on grade computations and locations and record findings.
When a Consultant Monitors for MDOT:
MDOT will check consultant documentation to assure the QA checks have been made and record findings.
MDOT will make random field checks as needed and record findings.
Field books and grade computations are to be made available on request and become part of the project records upon completion of the project.
Design/Build Projects:
Details will be spelled out in the scope of the project. When no detailed information is given, the project responsibilities will revert to the standard specifications and current special provisions.
Drainage Staking Standards
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Stakes are to be measured to the nearest 0.1 foot.
Grade elevations will be staked to the nearest 0.01 foot.
Utility Stakes
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Stakes will be set at 50 foot intervals when placing new utility lines. Other utility stakes will be placed, as needed, to avoid conflicts with construction work. Stakes are usually graded to the nearest 0.1 foot. The extent of the staking will depend upon the utility work. Be sure to check proposed road or bridge grades and alignment for any possible conflicts with the utility work. Utility companies should be contacted to identify the location of underground utilities. Depths of utility lines should also be identified during this operation.
Utility Staking Responsibilities
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MDOT Staking Projects:
MDOT will make all necessary field checks and compute grades and locations.
MDOT will set stakes at least every 50 feet.
Stakes will indicate MDOT work and utilities will need to move accordingly.
Consultant Staking for MDOT (project staking):
Consultant will make all necessary field checks and compute grades and locations and present data to the MDOT Engineer prior to staking.
MDOT will make random QA checks at the frequency required and record findings.
MDOT will make random QA checks on the computations and record findings.
All field data and computations are to be made available on request and become part of the project records upon completion of the project.
Contractor Staking Projects:
MDOT will do utility staking until the contract is awarded.
After award, the Contractor is responsible for gathering field data and computing grades for presentation to MDOT prior to staking.
Contractor will set necessary stakes at least every 50 feet.
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random QA checks on computations and record findings.
When a Consultant Monitors for MDOT:
MDOT will check documentation to assure the QA checks have been made and record findings.
MDOT will make random field checks as needed and record findings. Field data and computations are to be made available on request and become part of the project records upon completion of the project.
Design/Build Projects:
Details will be spelled out in the scope of the project. When no detailed information is given, the project responsibilities will revert to the standard specifications and current special provisions.
Utility Staking Standards
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Stakes are to be measured to the nearest 0.1 foot.
Grade elevations will be staked to the nearest 0.1 foot.
Tunnel Stakes
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Tunnel stakes for alignment and grade will be set at each shaft. This will enable preset surface alignment to be accurately transferred into the tunnel. Shafts shall be drilled a minimum of every 1000 feet on straight sections and as required on each curve. Additional alignment shafts may be required by the Engineer.
Tunnel Staking Responsibilities
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MDOT will determine how the project is to be staked depending upon staff availability.
MDOT Staking Projects:
MDOT will develop all necessary line and grade information.
MDOT will set initial line and grade in the shaft. Additional alignment will be required in vertical holes at least every 1000 feet and at all curves.
Stakes will indicate cut to flow lines and offset information.
Consultant Staking for MDOT (project staking):
Consultant will compute all line and grade information and present to MDOT Engineer prior to staking.
Consultant will set stakes as noted under MDOT staking.
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random QA checks on the grade and alignment computations and record findings.
Field books and grade computations are to be made available on request and become part of the project records upon completion of the project.
Contractor Staking Projects:
Contractor will compute all line and grade information and present to the MDOT Engineer prior to staking.
Contractor will set stakes as noted under MDOT staking.
MDOT will make random QA field checks at the frequency required and record findings.
MDOT will make random QA checks on grade and alignment computations and record findings.
When a Consultant Monitors for MDOT:
MDOT will check documentation to assure the QA checks have been made and record findings.
MDOT will make random field checks as needed and record findings.
Field books and grade computations are to be made available on request and become part of the project records upon completion of the project.
Design/Build Projects:
Details will be spelled out in the scope of the project. When no detailed information is given, the project responsibilities revert to the standard specifications and current special provisions.
Tunnel Staking Standards
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Stakes are to be measured to the nearest 0.1 foot.
Grade elevations will be staked to the nearest 0.1 foot.
Miscellaneous Stakes
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Muck stakes will generally be set at the time of cross sectioning. Staking will be done according to the current standards. Offsets should be discussed with the Contractor. Usually, lath stakes will be used for this staking.
Items such as guardrail, signs, etc., will normally not be staked by MDOT as long as there is pavement or curb and gutter next to the work.
Topographic information may need to be collected for design. Normally, this is done electronically using data collectors. Care is needed to use the proper coding so the computer interprets the data properly. There are different data collectors and software to process the data. CaiCE is the current software package being used to edit data before sending it to design. Contact the Region surveyor or Lansing Construction and Technology for assistance. Coding currently being used for electronic data collection is shown on the following pages. Suggested changes or additions should be sent to Design Surveys in Lansing.
Miscellaneous Staking Responsibilities
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Contractor will be responsible for line and grade for miscellaneous items, such as guardrail, signing, etc.
MDOT will make random QA checks and record findings.
Miscellaneous Staking Standards
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Stake locations are to be measured to the nearest 0.1 foot.
Grade elevations will be staked to the nearest 0.1 foot.
Bridge Staking
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The Engineer will furnish a stakeout diagram or a baseline and reference point coordinates for each bridge and box culvert. Information on the stakeout diagram will include construction centerline, reference lines and two bench marks. Witnesses for each reference point will also be shown. The original sketch will be kept in the project files. In addition to the stakeout diagram, a general sketch showing the points necessary to find the bridge centerline and the construction centerline is generally placed in the bridge layout field book.
Figures 104-45, 104 46 and 104-47 are examples of stakeout diagrams, or layout with coordinates.
Before starting a bridge stakeout, the transit/total station should be checked to be sure it is in proper working adjustment. Particular attention needs to be paid to the ability of the instrument to double center.
The stakeout can be parallel to bridge construction centerline, perpendicular to the reference line, or a combination of these. Structure can also be staked by use of coordinates. Standard temperature and slope corrections must be taken into account if a drag chain is used. A minimum of two angles will need to be turned. The number of repetitions will depend on the instrument being used. After the stakeout is complete checks can be established by extending the reference lines and bridge centerline in order to measure diagonals or to measure angles and distances along each pier or reference line.
The Contractor is responsible for setting line and grade for each foundation and the Engineer will verify. The Contractor will then set all line and grade to the bridge seat. All grades are to be set to the nearest 0.01 foot. Before pouring the pier cap or abutment, the Engineer will check line, grade and span lengths. Grade and alignment checks are to be documented in a field book.
The Contractor is responsible for all beam shots and deck grade computations, including screed and bulkhead grades. However, before any pours or adjustments to the grades are made, they are to be presented to the Engineer for review. Dry runs still need to be made and documented by the Contractor.
Bridge Staking Responsibilities
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MDOT OR THEIR REPRESENTATIVE:
Will stakeout the structure and provide a stakeout diagram with witnesses
or
Stakeout reference points, a baseline and develop coordinates if this method is desired by the Contractor.
Provide a minimum of two benchmarks.
Verify line and grade of footings prior to making pours.
Verify line and grade for abutments, piers and pier caps prior to making pours.
Check span lengths and location of position dowels.
Make random QA field checks at the frequency required.
Make random QA checks on alignment and grade computations.
Make random computation checks for pay quantities such as earthwork.
Document findings of all checks (field and computation).
After structure is complete, measure clearance and document on Form 1190 (Figure 104-48). See instructions for filling out this form on following pages.
Contractor:
Preserve witnesses and benchmarks.
Develop all grades, alignment, dimensions and provide to the Engineer prior to staking, including clearance checks and deck grades.
Take beam shots for determining deck, bulkhead and screed grades.
Set position dowels.
Take all cross sections, make plots and compute earthwork quantities.
Field books and computations are to be made available on request and become part of the project records upon completion of the project.
Design/Build Projects:
Details will be spelled out in the scope of the project. When no detailed information is given, the project responsibilities will revert to the standard specifications and current special provisions.
Bridge Staking Standards
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Stake locations are to be measured to the nearest 0.01 foot.
All grade elevations will be staked to the nearest 0.01 foot.
Cross section distances will be measured to the nearest 0.1 foot.
Cross section elevations will be read to the nearest 0.1 foot.
Reporting Structure Clearances
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It is necessary to measure and report altered clearances. This needs to be done in the case of new construction, or improvement of existing roadway or structures. Use Clearance Measurements, Form 1190. The procedures are outlined here.
Trunkline Over
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Submit the completed form when the deck is complete, and/or the road under is paved or resurfaced. If the project is not to be opened yet, leave the date blank (note in remarks that a later report will be submitted). The clearance must be signed if less than 16 feet.
Trunkline Under
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Submit the completed form when the roadway is paved. If the project is not to be opened yet, leave the date blank (note in the remarks that a later report will be submitted). Upon completion of the work, a revised 1190 is to be submitted.
Any restriction that is to occur that is less than the existing situation must be signed by the Contractor and the permit section notified.
If the reduction in clearance is temporary, effective dates and approximate length of time should be given with a follow-up report for clearances on the next stage of the work.
When the work under the structure is complete to the point where no more changes in dimensions will occur, such as dead load deflection, or the addition of a concrete median barrier, submit the form again. If the open to traffic date can be reasonably and accurately determined, this can be the final report. If not, a later one may still be required.
Roadway Over Railroads
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One report at the time the roadway is opened to traffic is needed. Complete information regarding clearances for the railroad must be included.
Roadway Over Streams
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There is no detailed clearance reporting required on the common stream crossing. The clearances for channels will be taken from the plans. Open to traffic date is the only requirement for Form 1190 in these instances.
Existing signs, where available, and if the legend is valid, may be reused during construction by relocating them at the appropriate time. If there is no change in the clearance at this time, new clearance reporting is not necessary. However, reporting open to traffic dates on the deck is important. If the new deck is partial width, this should be noted for the structure inventory. When work is completed, new measurements and Form 1190 need to be submitted.
Detailed instructions for filling out Form 1190 are included in this section. Item numbers refer to the blocks on the form where specific information is entered. Refer to the diagrams on the back side of the form (Figure 104-48) and to the examples of horizontal and vertical clearance measurements in (Figure 104-49).
Instructions for Filling Out Form 1190
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The measurements for right and left are to be taken as if looking in the direction of stationing. In general, this is to the east or north. All structures on the entire route are inventoried sequentially in the same direction.
Generally, even numbered routes run east and west with odd numbered routes running north and south. Business loops are inventoried in the same direction as the main route. Spur roads (penetrators) are usually inventoried as a separate route.
Dual, but conflicting, routes are inventoried as if the higher priority route controls. Fill in the route number with the prime route and put the secondary route number in parentheses. Ramp structures are identified using route numbers connected, direction and quadrant designation.
The direction of inventory is shown on the sketches for each control section in the roadway sufficiency rating report. If you cannot make the determination, contact the Region office for assistance.
Item 54 Minimum Vertical Underclearances
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LEFT (x) code, (xxxx) FFII, RIGHT (x) code, ( xxxx) FFII.
For the left and right openings, record the reference feature and the minimum vertical clearance from the roadway (travel lanes only) or railroad track beneath the structure to the underside of the superstructure. When both a railroad and highway are under the structure, record the most critical dimension.
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Reference Feature |
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Minimum Vertical clearance (left) |
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Reference Feature |
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Minimum Vertical clearance (right) |
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Using the codes below, code the reference feature from which the clearance measurement is taken.
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Highway beneath structure. |
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Railroad beneath structure. |
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Feature other than highway or railroad. |
Using up to 4 digits, record the minimum vertical clearance from the feature to the structure, rounded down to the nearest inch. When a restriction is 100 feet or greater, record 9999. If the feature is not a highway or railroad, leave blank.
Note: In Michigan, the minimum underclearance is measured as the difference in elevation from the pavement to the lowest overhead obstruction at a point 2 feet off the edge of pavement to compensate for vehicle overhang, unless the underclearance at some point on the pavement is less.
Examples:
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Railroad, 31 '- 3" & 34' - 6" beneath structure |
R 3103 |
R 3406 |
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Highway, 34' - 4" beneath structure |
H |
H 3404 |
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River, beneath structure |
N |
N |
Item 117 Vertical Clearance Route Under Best 10 feet
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LEFT (xxxx) FFII, RIGHT (xxxx) FFII.
This item pertains to the roadway under the structure. It applies only to the clearance under a structure.
For the left and right openings over the inventory route. A record the minimum vertical clearance(s). The minimum clearance for a 10 foot width of the pavement, or traveled part of the roadway where the clearance is the greatest, shall be recorded using up to 4 digits, rounded down to the inch. For structures with multiple facilities passing under, clearance for each facility shall be measured, but only the greatest of the "minimum clearances" for the two or more facilities shall be recorded, regardless of the direction of travel (see note below). This would be the practical maximum clearance. When no restriction exists, or when the restriction is 100 feet or greater, record 9999.
Note: If multiple facilities pass under the structure, record the clearance for each facility in the REMARKS area of the inventory form and record the clearance for only the facility determined most important, according to this table.
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State highway, business route or loop. |
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County highway or city street. |
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Ramp, wye or service road. |
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Other roads. |
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Railroads. |
For a single two-way roadway situation, record Left as blank and record Right with the clearance.
For multiple roadway situations, record clearances for Left and Right openings in their respective boxes.
Left and Right are determined with respect to the inventory direction.
Examples:
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Item 147 Inventory Route Under, Total Horizontal Clearance
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LEFT (xx.x) feet, RIGHT (xx.x) feet
This item is recorded only for roadway(s) or railroad which passes beneath the structure.
Record the total horizontal clearance for the left and right openings of the inventory route, or railroad(s) beneath the structure. The clearance should be the available clearance measured between the restrictive features - curbs, rails, walls, or other structural features; limiting the roadway (surface and shoulders). The measurement should be recorded using up to 3 digits, rounded down to the nearest tenth of a foot. When the restriction is 100 feet or greater, record 99.9.
The purpose of this item is to give the largest available clearance for the movement of wide loads. Flush and mountable medians are not considered restrictions. This clearance is defined in two ways, use the most applicable.
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Clear distance between restrictions of the inventory route “under” the structure. |
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If multiple facilities pass beneath the structure, record the horizontal clearances in the REMARKS area of the inventory form; record the clearance for only the facility determined most important, according to this table :
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State highway, business route or loop. |
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County highway or city street. |
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Ramp, wye or service road. |
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Other roads. |
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Railroads. |
For a single two-way roadway situation, record Left as blank and record Right with the clearance.
For multiple roadway situations, record clearances for Left and Right openings in their respective boxes.
Examples:
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Item 55 Minimum Lateral Underclearance on Right
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(x) code, (xx.x) feet
Record the reference feature and the minimum lateral underclearance on the right. When both a railroad and highway are under the structure, record the most critical dimension (refer to Item 69 - Underclearance, Horizontal - Table 3B).
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Reference feature. |
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Minimum Lateral clearance. |
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Using the codes below, record in the reference feature from which the clearance measurement is taken.
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Highway beneath structure. |
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Railroad beneath structure. |
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Using up to 3 digits, record the minimum lateral underclearance on the right to the nearest tenth of a meter. The lateral clearance should be measured from the right edge of the roadway (excluding shoulders), or from the centerline (between rails) of the right-hand track of a railroad, to the nearest substructure unit (pier, abutment, etc.), to a rigid barrier (concrete bridge rail, etc.), or to the toe of slope steeper than 1:3, e.g., 1:1 or 2:1. The clearance measurements to be recorded will be the minimum after measuring the clearance in both directions of travel. For a dual highway, this would mean the outside clearances of both roadways should be measured and the smaller distance recorded.
If two related features are below the bridge, measure both and record the lesser of the two. An explanation of what was recorded should be written on the inspection form. When the clearance is 100 feet or greater, record 99.9.
If the feature beneath the structure is not a railroad or highway, record N and leave measurement blank to indicate not applicable.
The presence of ramps; and acceleration or turning lanes, is not considered in this item; therefore, the minimum lateral clearance on the right should be measured from the right edge of the through roadway.
Examples:
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Railroad 20.41 feet, centerline to pier. |
R 20.4 |
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Highway 53.02 feet, edge of pavement to pier. |
H 53.0 |
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Creek beneath structure. |
N |
Item 56 Minimum Lateral Underclearances on Left
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(xx.x) feet
Record only for divided highways, one-way streets and ramps, not applicable to railroads.
Using up to 3 digits, record the minimum lateral underclearance on the left (median side for divided highways) to the nearest tenth of a foot.
The lateral clearance should be measured from the left edge of the roadway (excluding shoulders) to the nearest substructure unit, to a rigid barrier, or to the toe of slope steeper than 1:3. Refer to examples on previous page under Item 55 - Minimum Lateral Underclearance on Right.
For a dual highway, the median side clearances of both roadways should be measured and the smaller distance recorded. If there is no obstruction in the median area, a notation of "open" should be recorded and 99.9 should be recorded. For clearances greater than 100 feet, record 99.9. Record as blank to indicate not applicable.
Items 58 - 62 Condition Ratings
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To promote uniformity between bridge inspectors, these guidelines will be used to rate and code items 58, 59, 60, 61 and 62.
Condition ratings are used to describe the existing, in-place bridge as compared with the as-built condition. Evaluation is for the materials related, physical condition of the deck, superstructure and substructure components of a bridge. The condition evaluations of channels and channel protection and culverts are also included. Condition codes are properly used when they provide an overall characterization of the general condition of the entire component being rated. Conversely, they are improperly used if they attempt to describe localized, or nominally occurring instances, of deterioration or disrepair. Correct assignment of a condition code must, therefore, consider both the severity of the deterioration or disrepair, and the extent to which it is widespread throughout the component being rated.
The load-carrying capacity will not be used in evaluating condition items. The fact that a bridge was designed for less than current legal loads and may be posted shall have no influence upon condition ratings.
Portions of bridges that are being supported or strengthened by temporary members will be rated based upon their actual condition; that is, the temporary members are not considered in the rating of the item (Item 103 - Temporary Structure Designation for the definition of a temporary bridge).
Completed bridges not yet opened to traffic, if rated, shall be coded as if open to traffic. A rating of 9 shall be given to new structures or reconstructions after project bid letting.
Item 53 Minimum Vertical Clearance Over Bridge Roadway
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(xxxx) feet
Record, using up to 4 digits, the actual minimum vertical clearance over the bridge roadway, including shoulders, to any superstructure restriction, rounded down to the nearest inch. For double-decked structures, record the minimum regardless of whether it is pertaining to the top or bottom deck. When no superstructure restriction exists above the bridge roadway, or when a restriction is 100 feet or greater, record 9999.
Examples:
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Item 10 Vertical Clearance Route Over Best 10 feet
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LEFT (xxxx) FFII, RIGHT (xxxx) FFII.
This item pertains to the roadway carried by the structure and is blank if Item 5 is blank. This applies only to the clearance over a structure.
For the left and right roadways, record the minimum vertical clearance(s) over the inventory route identified in Item 5. The minimum clearance is for a 10 foot width of the pavement, or traveled part of the roadway, where the clearance is the greatest and shall be recorded using up to 4 digits, rounded down to the nearest inch. This would be the practical maximum clearance. When no restriction exists, or when the restriction is 100 feet or greater, record 9999.
If multiple facilities are carried by the structure, record the clearance for the facility determined most important, according to the table below. Record clearances for additional facilities in the REMARKS area of the inventory form.
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Interstate highway. |
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Other roads. |
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Railroads. |
For a single two-way roadway situation, record Left as blank and record Right with the clearance (and vice-versa) as shown below.
For multiple roadway situations, record clearances for Left and Right openings in their respective boxes as shown below.
Left and Right openings are determined with respect to the inventory direction.
Examples:
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When field checks indicate the item is out of tolerance, the adjacent grades on each side are to be checked. When computed grades are found to be wrong, the grade checks need to be extended in each direction until found to be correct. All utility and drainage must check into existing elevations. At no time will thin decks be allowed.
Consultant/Contractor Staking Quality Assurance Guidlines
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The number of checks noted below are considered to be the minimum to be taken over the life of the project. When things are going well the stated frequency is adequate. However, when things aren’t checking, more will be needed to determine the limits of the problem. The Engineer is responsible for ensuring that QA checks are done on every job and this is considered to be vital information. Results of all checks need to be documented, including name of checker and when checks were made.
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MDOT sets originally, but the resetting of them during various construction operations requires random checking. This would include bridge stakeouts, curve and spiral points. | ||||||
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Right-of-Way |
MDOT will normally establish ROW. When an outside agency stakes, MDOT will make random checks, including easements. | ||||||
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Benchmarks |
MDOT will establish vertical control. Random field checks of bench elevations are required to assure they have not been moved during the project. Also need to verify additional BM loops are checking properly, including field books. | ||||||
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Checks include grade sheets, computations and field books, including BM checks. | ||||||
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Slope Stakes Subgrade Stakes
Undercut Stakes Clearing Stakes |
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Pavement Stakes |
Checks include grade sheets, computations and field books, including BM checks. | ||||||
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Normal Sections Full Super |
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Drainage Stakes |
Checks include computation checks and field checks of existing flow lines. | ||||||
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Culverts Sewers Subsurface Drains Outlets Underdrains Railroads |
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Miscellaneous Staking |
Checks include computation checks and checks to existing elevations when appropriate. | ||||||
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Pump stations Tunnels Curb & Gutter Sidewalk Water Mains Retaining Walls Siphons Sound walls Junction Chambers Guardrail Sign Structures Signs Structure Crossovers Restoration Items Erosion Control Miscellaneous |
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Checks include grade sheet and plan computation checks. | |||
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MDOT will normally establish original alignment and vertical control. Random QA checks will still be needed as noted. Checks include haunch, deck, sidewalk, barrier grades, etc., computations and dry run results. Concerns are proper cross section and thin decks. | |||
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Substructure
Superstructure
Underclearance |
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Supplies and Equipment Paint Colors
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When painting removal items, grades, witness stakes, etc., only certain colors are to be used. The color that has been set aside for surveying activities is magenta (pink).
Paint Colors
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The following colors have been reserved for utility companies and should not be used for surveying.
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Oil and gas |
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Phone and CATV |
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Electric |
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Water |
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Sewer |
Care of Equipment
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Surveying instruments are expensive, sensitive, precision instruments and need to be handled with respect in order to retain their accuracy. They are subjected to dust, extreme temperatures, rain and snow. Therefore, they need to be cleaned and adjusted regularly in order to avoid excessive wear. Special measures need to be taken when transporting, even if only moving a short distance. In addition to the padded case the instruments come with, compartments should be constructed in trucks to minimize jarring while traveling. Never transport any instrument while still on the tripod. The more sensitive instruments, such as total stations or GPS units, should be placed on the floor behind the front seat. Carrying cases should be kept in good, clean condition. If the case cannot be repaired at the TSC level, contact Lansing Construction and Technology.
All surveying instruments should be checked at frequent intervals to ensure required accuracy. Permanent locations should be established for pegging levels, checking optical plums and calibrating measuring devices. A log on each instrument should be kept up to date and results of each check are to be noted (who, when, and where should also be noted).
MDOT maintains a location for cleaning, adjusting and repairing instruments at the Secondary Complex. Instruments should be checked at the end of each season and those needing cleaning or adjusting scheduled for service. When bringing instruments in for service, any problem area should be noted and damaged parts included. If the instrument is damaged, a complete written report giving all the circumstances must be included. If the damage is due to an accident on the part of the employee, the report should so indicate. If the damage was caused by the Contractor’s employees, or equipment, the report should reflect this information and the Contractor should be advised to refer the matter to his insurance company so they may inspect the damage if desired. If the instrument is damaged by the traveling public, this should be noted and an accident report included. The cost of instrument repair is often recoverable from motorist insurance companies.
Before operating surveying equipment, all MDOT personnel should be trained on proper operation and care of the instrument, including proper methods of transporting. Surveying equipment should not be left unattended at any time. Every means should be exercised to ensure the safety of both instrument and personnel while working in traffic, or near construction operations.
Field personnel should know the proper methods for care and field checking of survey instruments. These instructions; however, are not given with the intent that field personnel should attempt to make repairs or adjustments with which they are not thoroughly acquainted. It is much better to turn it in, along with a detailed explanation as to what appears to be wrong, so that trained personnel can make proper repairs.
Any electronic instrument needs to be turned off before moving locations. Any instrument that is going to be stored for any period of time should have its power source disconnected.
Instruments are to be stored in the office when not in use. Whenever an instrument gets wet, or is taken inside after working in cold conditions, it should be wiped off and have the case left open with the lens cap removed.
Transfer or Return of Equipment
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MDOT personnel can still obtain chains, tapes, tripods, rulers, etc., through the Lansing central warehouse. Surveying instruments, or special surveying items such as levels, transits, total stations, data collectors, etc., need to be budgeted for and such requests should be coordinated through Construction and Technology.
It is necessary that Form 2115, Property Transfer and Disposal Notice (T&D) be prepared and submitted to Finance with a copy to Construction and Technology when any tagged equipment is temporarily loaned, or permanently transferred from one location to another. This is very helpful in locating lost equipment. The location number is now what governs and not the Engineer (the Engineer can move and no T&D’s are necessary, unless the office is also moved).
When instruments are returned to Lansing Construction and Technology for repairs, a memo must accompany the instrument indicating what work is needed. If the instrument is returned because it is no longer needed, a memo to that effect must be sent, along with a T & D notice.
Some instruments, such as total stations, data collectors and digital levels, and GPS units are still assigned to Construction and Technology since every location does not need all equipment every year or a location may need more than one piece of equipment.
Transporting Instruments in the Field
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During field operations, older style transits (vernier) and levels (dumpy) may be carried on the tripod. New style instruments, such as levels (automatic, lasers, digital), transits (electronic), total stations (all types) that use 5/8 x 11 flat heads, should never be transported on the tripod.
The Telescope
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To ensure a clear image in a telescope of a survey instrument, it is important that the external surfaces of the eyepiece and objective lenses be free from grit and film. If the image appears foggy, the external surface of the eyepiece lens needs cleaning. Dust may be removed with a fine camel=s hair brush (this should be in the case). To remove sticky or greasy matter, use a clean, chamois cloth (chamois should be in the case). Take care not to scratch the lens by wiping too hard. Water should be tried first to remove excess dirt. If water does not work try alcohol, but do not use too much, as it may cause the two lenses of the objective to separate (alcohol will dissolve the cement that holds them together). Wipe the lens dry and use a clean part of a chamois for each part of the lens to avoid scratching. Brush the lens again when dry.
Caution! Do not remove lenses. Unscrewing or removing the objective lens may affect the collimation, or line of sight, of the instrument. Excessive cleaning of the lens may eventually cause dimness of the image. Protect the lens as much as possible from exposure to dust and dampness. Keep the cap placed over the object lens except when the instrument is in use, the lens will last much longer.
When the telescope is being used, the sunshade should be in place to prevent troublesome reflections that would make vision difficult, and to protect the lens from the direct rays of the sun. The instrument is not perfectly balanced without the sunshade. In case of rain, place the rain cover over the instrument.
If the focus slide seems to work too hard, it is generally caused by the lubricant on the pinion hardening, or dirt in the instrument. The instrument should be taken in for repairs.
Cross Hairs
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Having an experienced repair person make any cross hair adjustments is best. However, if it becomes necessary to make adjustments, such as when two-pegging levels, be sure the screws are snug but not too tight. Loosen the opposing capstan screw before tightening for adjustment. Failing to do this might result in damaging the reticle, breaking the capstan screw, or possibly bending the telescope tube.
Tripod
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The tripod legs should not be allowed to become loose; the wing nuts and bolts at the head of the tripod should be tightened. When a tripod leg is allowed to fall of its own weight, it should sink slowly to the ground not drop suddenly. The shoes should be examined to see if they are loose. The screws should be set up tightly. The points of the shoes should be sharpened or replaced whenever necessary. The tripod cap should be in place whenever the tripod is not in use; this protects the threads.
NiCd Batteries
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NiCd rechargeable batteries tend to develop a memory if recharged after the same amount of use each time. Therefore, they should occasionally be run down completely before recharging. Do not charge after every use, particularly if used only for a short period of time.
If any instrument is going to be stored for more than a couple of weeks, the batteries need to be removed from the instrument. This holds true for NiCd or alkaline.
Field Checks for Total Stations
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Total stations are very sensitive instruments and field adjustments are not recommended. However, the cross hairs, standards, optical plummet, angle checking, etc., can be field checked the same as with the transits. Collimation can be checked electronically on some total stations (see manual). Total stations should be checked on a USGS baseline at least twice a year. The Lansing Construction and Technology Support Area should be contacted whenever there is a problem, or if the instrument is going to be available for a while. They will put the instrument on a stand to check it out and take it to a USGS baseline to check distance measuring.
The total stations should never be left on the tripod when transporting, never pointed directly at the sun, and batteries should be removed when the instrument is not in use. The operator should make note of the prism constant setting after it has been checked out on a USGS baseline and each day before using. The weather conditions (temperature and barometric pressure) should be entered into the instrument before using.
Measurements should be taken at least twice to ensure the instrument has been sighted on the proper prism. When using to transfer bench marks or looping, measurements need to be taken in the direct and inverted positions, then use the average. Use extreme care to sight the center of the prism because the vertical angle becomes critical.
Dumpy Level
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In order to prevent errors due to parallax, each instrument operator should carefully focus the eyepiece on the cross hairs until the hairs appear sharp. |
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This adjustment may have to be repeated as the distance between instrument and rod changes. |
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After leveling the instrument, one end of the horizontal hair is set on a sharply defined point. |
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Rotate the telescope slowly and the point should stay on the horizontal hair throughout its length. |
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If the point moves off the cross hair, the instrument can still be used as long as you always use the same spot on the horizontal cross hair whenever sighting. Send the level in for adjustment as soon as it is practical. |
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Center the bubble exactly in two directions. |
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Rotate the instrument 180 degrees. |
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If the bubble does not stay centered, the instrument is out of adjustment. The instrument can still be used, but you need to be sure the instrument is level when taking any reading. |
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Establish two points approximately 125 feet apart. Set up the instrument in the middle. |
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Take readings on each point. The difference will be the true difference. |
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Move the instrument near one point (the highest point is desirable). The closer, the better, but you need to be able to focus on the rod. |
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Take a reading on the near rod, add the true difference (if setting near the highest point) and this is what should be read on the far rod. |
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The difference between the actual reading on the far rod and the computed value is the amount of error. If the error is 0.02 foot or more, the check should be repeated. If the error continues to be 0.02 foot or more, the level should be sent in for repairs. |
Self-Leveling Levels
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Focusing, alignment of cross hairs and two-peg checks are the same as for the dumpy level. Since this instrument has a bull’s-eye type level instead of level vials, level the instrument, rotate it 90, 180 and 270 degrees, and check to see if the bubble moves out of the circle. If it does, the instrument should be sent in for adjustment.
Laser Levels
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Not many checks need to be made on the laser level in the field. There are no cross hairs to check, the instrument is not rotated so the bubble cannot be checked and no focusing is required.
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The two-peg check should be made periodically. What you are checking is the x-axis and the y-axis. |
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Set the rod on a point approximately 300 feet away and take a reading. |
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After taking a reading, rotate the instrument 90 degrees and take a reading. |
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Continue to rotate the instrument taking readings at 180 and 270 degrees. |
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If the instrument is in proper adjustment, all four readings should be the same. If the first and third readings are the same, the one axis is okay; if the second and fourth readings are the same, the other axis is okay. If the difference between the highest and lowest readings varies by 0.02 foot or more, the level should be sent in for repairs. |
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This method should be used if looping between bench marks with both readings recorded and the average used in the computations. |
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Take a reading by moving the receiver up from the bottom until on target. |
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Take another reading by moving the receiver down from the top until on target. |
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The difference should be noted. If the difference is more than 0.02 foot, the level needs to be adjusted. |
Digital Level
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The only field checks to make on the digital level are the bull’s-eye level bubble and the two-peg. The bubble check is the same as with the self-leveling level. The two-peg is performed the same way as with any level. When operating a digital level, be aware of the following.
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Be sure to focus clearly. |
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The rod must be held steady. |
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300 feet is the maximum sighting distance. |
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Approximately two-thirds of the rod must be visible. |
Field Checks for the Transit and Theodolite
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Center the plate bubbles. |
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Rotate the instrument 180 degrees. |
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If the bubbles do not remain in the center, send in for repairs. |
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On instruments with only one bubble, level in two directions. |
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Rotate the instrument 180 degrees and check. |
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If the instrument is off more than one graduation, it should be put on a stand and adjusted. |
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The bubble on instruments with bulls-eye bubble is less sensitive than the plate bubbles but should be checked as the instrument is rotated (should stay inside the circle). |
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This is a very important check; if out of adjustment very far, accurate angles cannot be turned. |
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After leveling the instrument, set one end of the vertical wire on a sharply defined point. |
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Move the telescope up or down and the point should stay on the vertical cross hair. |
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If the point moves off the cross hair, the instrument can still be used as long as you always use the same spot on the vertical cross hair whenever sighting. Send the instrument in for adjustment as soon as it is practical. |
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Sight on a point at least 200 feet in front of transit |
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Plunge the telescope and set a point at approximately the same distance and elevation in the other direction. |
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Rotate the telescope 180 degrees (horizontally) back to first point. |
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Plunge the telescope and recheck the second point. |
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If the distance is more than 0.02 foot off in 200 feet, the instrument should be sent in for adjustments. |
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Level the instrument and sight on a high point. |
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Rotate the telescope and set a point as close as possible in front of the instrument. |
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Plunge the telescope; rotate 180 degrees (horizontally) and sight back to the high point. |
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Rotate the telescope down and check the point set in front of the instrument. |
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Level the instrument over a point; rotate the instrument while observing the point. If the center does not move off the point the instrument is in adjustment. The more the center moves off the point the more error there is in the horizontal angle. If out of adjustment, the instrument must be adjusted on a repair stand. |
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Another way to check this is to level the instrument over a point using a plumb bob. Remove the plumb bob and check the optical plummet in various positions. |
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The angle turning ability is checked in the field by “closing the horizon” or turning angles in a full circle then adding up the angles to see how well they check with 360 degrees. |
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CODE |
DESCRIPTION |
DTM |
CODE |
DESCRIPTION |
DTM |
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ABUT |
Bridge Abutment |
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CTV |
Cable TV (UG) |
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ALI |
Alignment Pt |
|
DAM |
Dam |
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ANC |
Deadman |
|
DCH |
Ditch Centerline |
|
|
AZM |
Azimuth Mark |
|
DECK |
Bridge Deck |
|
|
BB |
Bottom of Bank |
|
DIKE |
Dike |
|
|
BC |
Back of Curb |
|
DLOT |
Dirt Lot |
|
|
BDR |
Bit Drive |
|
DRV |
Surfaced Drive |
|
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BEAM |
Beam |
|
EB |
Edge of Bituminous |
|
|
BFR |
Big Rock |
|
EC |
Edge of Concrete |
|
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BIKE |
Bikeway/Path |
|
EG |
Edge of Gravel |
|
|
BLD |
Building |
|
ELHH |
Elec Handhole |
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BLOT |
Bit Lot |
|
ELMH |
Elec Manhole |
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BRL |
Brush Line |
|
ELO |
Elec Line Overhead |
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BRR |
Concrete Barrier |
|
ELU |
Electric Line (UG) |
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BSH |
Bush |
|
EM |
Edge of Metal |
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CB |
Catch Basin |
|
EP |
Edge of Pavement |
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CC |
Curb Cut |
|
ETB |
Elec Trans Box |
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CDR |
Concrete Drive |
|
EW |
Edge of Water |
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CEM |
Cemetery |
|
EWL |
Edge of Wetland |
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CL |
Centerline (Generic) |
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FCOR |
Fence Corner |
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CLB |
Centerline (Bridge) |
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FL |
Flow Line |
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CLOT |
Concrete Lot |
|
FLAG |
Flag Pole |
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CLV |
Culvert (Generic) |
|
FNC |
Fence Line |
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CMP |
Corr Metal Pipe |
|
FOP |
Fiber Optic Cable |
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CP |
Traverse CTL Line |
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FTG |
Footing |
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CRK |
Creek CL |
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GAS |
Gas Line (Natural) |
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CTRS |
Center Section Corner (PLS) |
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GDR |
Gravel Drive |
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GFP |
Gas Filler Pipe |
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MH |
Manhole |
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GLM |
Gas Line Marker |
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MISC |
Miscellaneous Line |
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GLOT |
Gravel Lot |
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MRSH |
Marsh Line |
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GPMP |
Gas Pumps |
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NGS |
NGS Monument |
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GPS |
GPS Monument |
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NOIS |
Noise Barrier Wall |
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GR |
Guardrail |
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NWLK |
Walk-No Walk Sign |
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GRG |
Garage |
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OCHD |
Orchard |
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GUT |
Gutter Flow Line |
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OIL |
Pipeline (Oil) |
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GVLV |
Gas Valve |
|
OWEL |
Oil Well |
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GTU |
Gas Tank (Undgrnd) |
|
PATH |
Path |
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GWEL |
Gas Well |
|
PH |
Telephone or Call Box |
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GYP |
Guy Pole |
|
PIER |
Pier |
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GYW |
Guy (Deadman) |
|
PIN |
Iron Pin |
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H2O |
(UG) Watermain |
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PINE |
Conifer Tree |
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HDG |
Hedge Line |
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PIPE |
Iron Pipe |
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HI |
High Points |
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PK |
PK Nail |
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HSE |
House |
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PLAT |
Plat Boundary |
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HVCP |
Photo Target |
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PLP |
Power Light Pole |
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HWAL |
Headwall |
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POLE |
Utility Pole (Generic) |
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HYD |
Fire Hydrant |
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POND |
Pond |
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LAKE |
Lake |
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POST |
Post (Generic) |
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LBASE |
Light Base |
|
PP |
Power Pole |
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LBOT |
Lake Bottom (PNT) |
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PROP |
Property Line |
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LL |
Lane Line |
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PTWR |
Power Tower |
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LO |
Low Points |
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PVT |
Surfaced Roads |
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LP |
Light Pole |
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QCOR |
Quarter Section Corner (PLS) |
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MB |
Mailbox |
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QQCOR |
Sixteenth Corner (PLS) |
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MBOX |
Monument Box |
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RBOT |
River Bottom (PT) |
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MEAN |
Meander Cor (PLS) |
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RCP |
RNFC Concrete Pipe |
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RDG |
Ridge/Break Line |
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STMH |
Storm MH |
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REFL |
Reference Line |
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STMP |
Stump |
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RFPT |
Reference PT |
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STR |
Structure |
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RIP |
Riprap |
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STRM |
Stream Centerline |
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RM |
Reference Mark |
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SW |
Sidewalk |
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ROC |
Rock Outcropping |
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TB |
Top of Bank |
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RR |
Railroad Tracks |
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TELO |
Telephone (OVHD) |
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RRSG |
RR Signal |
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TELU |
Telephone (UG) |
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RRSW |
RR Switch Box |
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TGRPH |
Telegraph (UG) |
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RTWL |
Retaining Wall |
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TMH |
Telephone MH |
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RV |
River Centerline |
|
TP |
Telephone Pole |
|
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RW |
Row Marker |
|
TPED |
Telephone PED |
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SAN |
San Sewer Line |
|
TREE |
Deciduous Tree |
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SCL |
Survey Centerline |
|
TREL |
Tree Line |
|
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SCOR |
Section Corner (PLS) |
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TRL |
Trail |
|
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SD |
Satellite Dish |
|
TSTHL |
Test Hole |
|
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SGN |
Sign Post |
|
UMH |
Util MH (Generic) |
|
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SHBL |
Shrub Line |
|
USGS |
USGS Mon |
|
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SHLD |
Shoulder |
|
VCP |
Vert Target |
|
|
SIG |
Traffic Signal |
|
WEIR |
Weir |
|
|
SLAB |
Concrete Slab |
|
WELL |
Well (Generic) |
|
|
SMH |
Sanitary MH |
|
WIT |
Witness Sec Corner (PLS) |
|
|
SNLI |
Sign/Billboard |
|
WSO |
Water Shutoff |
|
|
SPKHD |
Sprinkler Head |
|
WV |
Water Valve in Manhole |
|
|
SPL |
Spillway |
|
WWAL |
Wing Wall |
|
|
SS |
Storm Sewer Line |
|
WWEL |
Water Well |
|
|
STA |
Survey Station |
|
XYZ |
Random Shot (Spot Elev) |
|
|
STM |
Steamline (UG) |
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