Profile Leveling
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Profile Leveling
description
Profile Leveling. Definition. A surveying method that yields elevations at definite points along a reference line. Profile leveling establishes a side view or cross sectional view of the earth ’ s surface. Primary use is for utilities: Highways Canals Sewers Water mains Sidewalks - PowerPoint PPT Presentation
Transcript of Profile Leveling
Profile Leveling
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Definition
A surveying method that yields elevations at definite points along a reference line.
Profile leveling establishes a side view or cross sectional view of the earth’s surface
Primary use is for utilities:A. HighwaysB. CanalsC. SewersD. Water mainsE. SidewalksF. Retaining wallsG. Fences
All of these need accurate information about the topography along the route.
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Characteristics
May be straight segments connected
with curves.
May be multiple segments which change directions with angle points.
May be a single segment.
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Procedure
It is a common practice to use a procedure called stationing.
1. Stations are established at uniform distances along the route.
2. Standard station distance is 100 feet.
3. Half or quarter stations are used when the topography is very
variable.
4. The distance from the starting point to the station is used as the
station identification.
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Procedure-cont.
Intermediate foresights: foresights taken at stations that are not used as benchmarks or turning points.
Foresights are recorded at each standard station and at additional
stations as needed to define the topography of the route.
These foresights are called intermediate foresights.
Purpose is to define the topography along the route.
High points
Low points
Changes in slope
Critical points
Roads
Highway
Gutters
Sidewalks
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Procedure-cont.
When distances to foresights become too long or when the terrain obstructs the view of the instrument, turning points are established.
Foresights on turning points and benchmarks are true foresights.
Profile leveling is differential leveling with the addition of intermediate foresights.
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Profile Data Table
STA BS HI FS IFS ELEV
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Example One
Determine the profile for a proposed sidewalk that connects two existing sidewalks.
Step one: establish the standard stations.
Note: the last station is established even though it is not a
standard station.
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Example One-cont.
Step 2: Determine the sites for the critical features.
In this example, the critical features are the rapid change is slope at 337.5 and the road at 489.6. Note a station was al20 established at 546.4 to define the width of the road and any changes in elevation across the road.
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Example 1-cont.
Step 3: Set up the instrument and start recording data.
The first rod reading is a backsight on the first sidewalk (benchmark) to establish the height of the instrument.
Note: in this case the true elevation of the benchmark is unknown, therefore 100.00 feet is used.
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Example One Data Table
STA BS HI FS IFS ELEV
0.0 10.5 110.5 100.00
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Example One-cont.
Step 4: Start recording the rod readings for each station.
Note: this station is not used as a benchmark or as a turning point, therefore is is an intermediate foresight.
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Example One Data Table
STA BS HI FS IFS ELEV
0.0 10.5 110.5 100.0
100 6.3 104.2
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Example One-cont.
The rod reading for each station is recorded on the appropriate line of the table.
STA BS HI FS IFS ELEV
0.0 10.5 110.5 100.0
100 6.3 104.2
200 3.9 106.6
300 4.1 106.4
337.5 7.4 103.1
400 9.2 101.3
489.6 8.0 102.5
Note: the rod reading for station 489.6 is placed in the FS column because this station will be used as a turning point.
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Example One-cont. Step 6: the instrument is moved so the remaining stations can be reached.
STA BS HI FS IFS ELEV0.0 10.5 110.5 100.0
100 6.3 104.2
200 3.9 106.6
300 4.1 106.4
337.5 7.4 103.1
400 9.2 101.3
489.6 6.6 109.1 8.0 102.5
500 6.7 102.5
546.4 6.8 102.2
600 4.9 104.2
700 2.2 106.9
745.1 1.5 107.6
Every time the instrument is moved, a backsight is used to reestablish the height.
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Example One-cont.
The last step is closing the loop.
STA BS HI FS IFS ELEV
0.0 10.5 110.5 100.0
100 6.3 104.2
200 3.9 106.6
300 4.1 106.4
337.5 7.4 103.1
400 9.2 101.3
489.6 6.6 109.1 8.0 102.5
500 6.7 102.5
546.4 6.8 102.2
600 4.9 104.2
700 2.2 106.9
745.1 2.3 109.9 1.5 107.6
TP2 8.3 111.4 6.8 103.1
0.0 11.5 99.9
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Note Check & Allowable ErrorSTA BS HI FS IFS ELEV
0.0 10.5 110.5 100.0
100 6.3 104.2
200 3.9 106.6
300 4.1 106.4
337.5 7.4 103.1
400 9.2 101.3
489.6 6.6 109.1 8.0 102.5
500 6.7 102.5
546.4 6.8 102.2
600 4.9 104.2
700 2.2 106.9
745.1 2.3 109.9 1.5 107.6
TP2 8.3 111.4 6.8 103.1
0.0 11.5 99.9
SUM 27.70 27.80
0.10 = 0.10
€
AE =k M = 1.0 x745.1 2x
5280 =0.5
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Plot of Profile Data
Sidewalk Profile
100.0
104.2
106.4
103.1
101.3
102.5102.3
104.2
106.9
107.6
102.4
106.6
99.5
100.0
100.5
101.0
101.5
102.0
102.5
103.0
103.5
104.0
104.5
105.0
105.5
106.0
106.5
107.0
107.5
108.0
0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750
Distance
Elevation
Potting the data helps answer questions as, “Will the slope of the sidewalk be acceptable?”.
In this example the steepest slope appears to be between stations 300 and 327.5. The slope at this point is:
€
% slope =Rise
Run 100 x =
106.4 - 103.1337.5 - 300.0
100x =3.337.5
100x =8.8 %
This is excessive slope according to ADA standards.
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Excel Calculation of Slope
Station Elevation % slope0.0 100.0
100.0 104.2 4.20200.0 106.6 2.40300.0 106.4 0.20337.5 103.1 8.80400.0 101.3 2.88489.6 102.5 1.34500.0 102.4 0.96546.4 102.3 0.22600.0 104.2 3.54700.0 106.9 2.70745.1 107.6 1.55
It is easy to calculate all of the slopes using a spreadsheet.
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Additional uses of Profile Plot
Profile plots are also very useful for other utility routes such as drain pipes.
Drains are design with a uniform slope.
Plotting the drain on the profile provides a visual of the relationship between the earth’s surface and the drain.
Assume the survey was completed for a drain pipe instead of a sidewalk.Also assume the starting elevation of the drain pipe is at three feet below the surface at station 0.0 and that the desired slope is 1%.
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Drain Plot
96.0
98.0
100.0
102.0
104.0
106.0
108.0
110.0
0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750
Distance
Elevation
Drain
Surface Profile
It should be oblivious that this design has problems because at station 550 the drain pipe is above ground.
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Drain Plot
96.0
98.0
100.0
102.0
104.0
106.0
108.0
110.0
0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750
Distance
Elevation
Drain
Surface Profile
One of the advantages of spread sheets is doing “What if” scenarios.What if the drain slope was changed to 0.5%?
The way this spread sheet was set up changing the % slope required change one value.
If the drain pipe will function correctly at 0.5% slope, this would be a workable alternative.
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Plots of profile data can be used for many other types of design questions.
What if the profile survey was for an open drain?In this situation questions like, “What is the maximum depth of the ditch can be determined?”.
At station 200 the elevation of the surface is 106.6 ft and the elevation of the bottom of the ditch is 98.0 ft. 106.6 - 98 = 8.6 ftThe ditch will be 8.6 feet deep at that point.
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This provides enough information to answer another design problem. How much space will be required for the ditch at the widest point?
The answer to this question is determined by the ditch design.Most drainage ditches have a trapezoidal cross section shape.The bottom width is determined by the anticipated flow rate through the ditch.The side slopes are usually either 2:1 or 3:1 ratio.Assuming a ditch bottom width of 15 ft.
The space required is 16 ft + 15 ft + 16 ft = 47 ft
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Questions
