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.

Intermediate foresights are recorded at each standard station and

at additional stations as needed to define the topography of the

route.

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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Defining an Object

• Because profile leveling is used to measure the cross section of and the location of objects along a route, one important issue is determining how many stations are required to define the object.

• The answer is, it depends on the object and the use of the data.

• For example: how many stations would be required to define the cross section of a standard trapezoidal ditch?

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Defining an Object-Ditch --cont

• A ditch may have been a trapezoid when constructed, but over time it will change its shape.

• What is the effect on the number of stations if a channel has developed in the bottom of the ditch?

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Defining An Object-Street

• Another common object is a street.• The number of stations required to define the

cross section of a street depends on the required information.– Do you need to know the height of the curb?– Do you need to know the width of the curb?

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Turning Points-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 and bisects a road.

Step one: establish the standard stations.

Note: the last station (745.1) 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 stations were established at 489.6 and 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: station 100 is not used as a benchmark or as a turning point, therefore it 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 instrument 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 x 745.1 x 2

5280 =0.5

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Profile With Side Benchmark

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Step 1• The principles are the same. • The difference is that in this case the BS is taken on the benchmark not

the first station.

The notes use the same column--they just start with the BM instead of 0.0.

STA BS HI FS IFS ELEVBM1 8.2 108.2 100.0

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Step 2• Record the first foresight. • In this example the first foresight (0+00) is an intermediate foresight.

STA BS HI FS IFS ELEV

BM1 8.2 108.2 100.0

0.0 9.2 99.0

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Step 3• Add additional intermediate foresights as needed until the first turning

point is reached.

STA BS HI FS IFS ELEVBM1 8.2 108.2 100.0

0.0 9.2 99.0

156.5 6.5 101.7

358.6 1.3 106.9

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Step 4• Move the instrument and continue recording foresights.

STA BS HI FS IFS ELEVBM1 8.2 108.2 100.0

0.0 9.2 99.0

156.5 6.5 101.7

358.6 2.1 109.0 1.3 106.9

458.6 5.2 103.8

522.6 7.7 101.3

598.2 5.4 103.6

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Step 5Close the loop

STA BS HI FS IFS ELEV

BM1 8.2 108.2 100.0

0.0 9.2 99.0

156.5 6.5 101.7

358.6 2.1 109.0 1.3 106.9

458.6 5.2 103.8

522.6 7.7 101.3

598.2 10.4 114.0 5.4 103.6

BM1 14.0 100.0

Sum 20.7 20.7

0 = 100.0-100.0 0

Note: close to the benchmark not station 0.0.

AE =K M =0.1 x 598.2 x 2

5280=0.047

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Questions?