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Applications• Stream cross sections• Highways• Canals• Sewers• Water mains• Sidewalks• Retaining walls• Fences

Application ofDifferential Leveling Introduction

Differential LevelingA surveying method that yields elevations at definite points along a reference line.Profile LevelingEstablishes a side view or cross sectional view of the earth’s surface

BAE 3313 Natural Resources Engineering

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Characteristics

Straight segments connected with curves

Multiple segments with changes in direction

Singlesegment

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ProcedureCommon practice to use a procedure called

stationing1. Stations are established at uniform

distances along a route, e.g. 100 feet2. Half or quarter stations are used when the

topography is very variable.3. The distance from the starting point to the

station is used as the station identification.

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Procedure - cont.

Foresights (FS) are recorded at each standard station

Intermediate foresights (IFS) Additional stations as needed to

accurately define the topography. Foresights (FS) taken at stations that are

not used as benchmarks (BM) or turning points (TP).

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When distances to foresights (FS) become too long or when the terrain obstructs the view of the instrument, turning points (TP) are established.

Profile leveling is differential leveling with the addition of intermediate foresights (IFS).

Procedure - cont.

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Profile Data Table

STA BS HI FS IFS ELEV

STA StationBS Back SiteHI Height of InstrumentFS ForesightIFS Intermediate ForesightELEV Elevation

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ExampleDetermine the profile for a proposed sidewalk

that connects two existing sidewalks.

Step One: establish standard stations

Note: last station is established even though it is not a standard station.

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Step 2: Determine sites for critical features

In this example, the critical features are the rapid change is slope at 337.5 ft and the road at 489.6 ft

Note: a station was established at 546.4 ft to define the width of the road and any changes in elevation across the road.

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Step 3: Set up instrument; start collecting data

First rod reading is a backsight (BS) on the first sidewalk (i.e. benchmark, BM) to establish the height of the instrument.

Note: the true elevation of the benchmark (BM) is unknown, therefore 100.00 feet is used.

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Example Data TableSTA BS HI FS IFS ELEV

0.0 10.5 110.5 100.00

STA StationBS Back SiteHI Height of InstrumentFS ForesightIFS Intermediate ForesightELEV Elevation

HI = ELEV + BS

ELEV = HI - FS

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Step 4: Start recording the rod readings at each station.

Note: this station is not used as a benchmark (BM) or as a turning point (TP), therefore it is an intermediate foresight (IFS).

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STA BS HI FS IFS ELEV

0.0 10.5 110.5 100.0100 6.3 104.2

Example Data Table

STA StationBS Back SiteHI Height of InstrumentFS ForesightIFS Intermediate ForesightELEV Elevation

HI = ELEV + BS

ELEV = HI - FS

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Rod reading for each station is recorded on the appropriate table line.

STA BS HI FS IFS ELEV0.0 10.5 110.5 100.0100 6.3 104.2200 3.9 106.6300 4.1 106.4337.5 7.4 103.1400 9.2 101.3489.6 8.0 102.5

Note: rod reading for station 489.6 ft is placed in the FS column because this station will be used as a turning point (TP).

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Step 5: 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 8.0 102.5500 6.7 102.5546.4 6.8 102.2600 4.9 104.2700 2.2 106.9745.1 1.5 107.6

Note: every time the instrument is moved, a backsight (BS) is used to reestablish the height of instrument (HI).

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Step 6: The last step is closing the loop

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 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 x 745.1 x 25280

=0.5

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Plot of Profile DataSidewalk Profile

100.0

104.2

106.4

103.1

101.3

102.5102.3

104.2

106.9

107.6

102.4

106.6

99.5100.0100.5101.0101.5102.0102.5103.0103.5104.0104.5105.0105.5106.0106.5107.0107.5108.0

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750Distance

Elev

atio

n

In this example the steepest slope appears to be between stations 300 and 327.5. The slope at this point is:

% slope = RiseRun

x 100 = 106.4 -103.1337.5 - 300.0

x 100 = 3.337.5

x 100 =8.8 %