Profile and Differential Leveling

1
Profile and Differential Leveling
AGME 1613Fundamentals of AST
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Objectives

• Define differential and profile leveling, and
  explain the purpose(s) and agricultural
  applications of each.
• Identify and correctly set-up and use leveling
  equipment.
• Properly record leveling field notes and perform
  error checks for differential and profile
  leveling surveys.
• Complete differential and profile leveling
  surveys.

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Leveling Definition and Types

• A surveying procedure used to determine the
  elevation of points on the Earths surface.
• Differential Leveling
• Profile Leveling

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Differential Leveling
Purpose is to determine the difference in
elevation between two (or more) points on the
Earths surface.
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Where is Differential Leveling Used?

• Determining field slope (conservation plans, soil
  loss prediction, etc.).
• Laying out and checking drainage ditches,
  waterways, tile drainage systems, etc.
• Cut-and-fill requirements for building
  foundations.
• Establish new benchmarks that have elevations
  tied in with existing benchmarks.

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Profile Leveling
Purpose is to describe the elevation at selected
points on the Earths surface.
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Where is Profile Leveling Used?

• Developing field contour maps.
• Designing and checking grade for drainage ditches
  and waterways.
• Laying out farm ponds.
• Road and highway construction.

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Leveling EquipmentThe Engineers Level

• Telescope with crosshairs.
• Base plate attaches level to tripod.
• Leveling screws allows user to establish a
  level line of sight.
• Level bubble Instrument is level when bubble is
  inside target.
• Focusing knob

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Leveling Equipment Tripod and Leveling Rod
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Reading the Leveling Rod
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Reading the Leveling Rod
Feet 6
Tenths .0
Hundredths .09
Reading 6.09 ft.
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Reading the Leveling Rod
3
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Direct Differential Leveling
What is the difference in elevation between two
points,
Where both points can be shot from the same
location?
6.45
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Direct Differential Leveling
3.21
B
A
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Direct Differential Leveling

• Difference in Elevation
• Rod reading at A 6.45
• Rod reading at B 3.21

Difference in elevation
3.24-ft
Which point is higher, A or B?
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Leveling Terms

• Station (STA)
• Benchmark (BM)
• Backsight (BS)
• Height of Instrument (HI)
• Foresight (FS)
• Elevation (ELEV)

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Leveling Terms

• Station (STA)
• Point where the rod is placed for a reading
• Stations typically use a distance-numbering
  identification system
• STA 0 00 0 hundred feet 0 feet
• STA 2 75 two hundred feet 75 feet
• STA 5 05 ?????????

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Leveling Terms

• Backsight
• A rod reading taken on a point of known
  elevation
• BM
• TBM
• Turning Point (TP)

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Leveling Terms

• Benchmark (BM)
• A point of known elevation used as a reference
  point in a leveling survey.
• A BM has a precisely known elevation above mean
  sea level.
• Established by a variety of government agencies.
  
• Temporary Benchmark (TBM) Point of assumed
  elevation. Commonly used in on-farm, local
  surveys.

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Leveling Terms

• Height of Instrument (HI)
• Height (elevation) of the levels line of sight.
• HI BS Known Elevation

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Determining HI
HI 100.00 ft 4.35 ft 104.35 ft
4.35
HI Elev BS
BM-1
Elev 100.00 ft.
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Leveling Terms

• Foresight (FS)
• Rod reading taken on a point of unknown elevation
• HI FS Elev

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Determining Elevation
HI 104.35 ft
6.35
Elev HI - FS
Elev 104.35 ft. 6.35 ft. 98.00 ft.
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Leveling Terms

• Elevation (ELEV)
• Vertical distance above mean sea level of a
  point on the earths surface.
• Depending on purpose of survey, may be determined
  to nearest
• .1 ft
• .01 ft.
• .001 ft.

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Differential Leveling Field Notes
STA BS HI FS ELEV Dist.







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Differential Leveling
3.21
TBM-1
BM-1
Elev 1225.50 ft.
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Differential Leveling
3.01
TBM-1
BM-1
TP-1
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Differential Leveling
6.04
TBM-1
BM-1
TP-1
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Differential Leveling
0.28
TBM-1
BM-1
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Differential Leveling
6.45
TBM-1
BM-1
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Differential Leveling
10.98
TBM-1
BM-1
TP-2
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Differential Leveling
3.95
TBM-1
BM-1
TP-2
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Differential Leveling
5.36
TBM-1
BM-1
TP-2
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Error of Closure

• Difference in the beginning and ending
  elevation of a known point.
• All surveys will have error.
• The question is, How much error can we tolerate
  in our survey?

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Error Check

• Mathematical Error Check
• Error of closure SBS - SFS
• Allowable Error Check
• Depends on purpose of the survey
• Maximum feet of error based on distance

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Profile Leveling Field Notes
STA BS HI FS ELEV







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Simulated Profile Survey
(Elev 100.00)
TBM-A
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STA. 000
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STA. 100
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STA. 135
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STA. 200
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STA. 200
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STA. 275
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STA. 295
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STA. 295
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