1. Profile and Differential Leveling
AGME 1613 Fundamentals of AST

2. 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.

3. Leveling Definition and Types
A surveying procedure used to determine the elevation of points on the Earth’s surface.
Differential Leveling
Profile Leveling

4. Differential Leveling
Purpose is to determine the difference in elevation between two (or more) points on the Earth’s surface. A B
Difference?

5. 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.

6. Profile Leveling
Purpose is to describe the elevation at selected points on the Earth’s surface. X A B

7. 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.

8. Leveling Equipment: The Engineer’s 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

9. Leveling Equipment: Tripod and Leveling Rod

10. Reading the Leveling Rod
Hundredths (.01) of a foot
Tenths (.10) of a foot
Feet

11. .10
.09
.08
.07
.06
.05
.04
.03
.02
.01
6.00-ft.

12. Reading the Leveling Rod
Feet = 6
Tenths = .0
Hundredths = .09
Crosshair
Reading = 6.09 ft.

13. Reading the Leveling Rod3

14. Direct Differential Leveling
“What is the difference in elevation between two points,
Where both points can be “shot” from the same location?”
6.45 B A

15. Direct Differential Leveling
3.21 B A

16. Direct Differential Leveling
Difference in Elevation
Rod reading at A =
Rod reading at B = -
Difference in elevation =
3.24-ft
Which point is higher, A or B? A B

17. Leveling Terms Station (STA) Benchmark (BM) Backsight (BS)
Height of Instrument (HI)
Foresight (FS)
Elevation (ELEV)

18. Leveling Terms Station (STA)
Point where the rod is placed for a reading
Stations typically use a “distance-numbering” identification system:
STA = 0 hundred feet + 0 feet
STA = two hundred feet feet
STA =?????????

19. Leveling Terms Backsight
A rod reading taken on a point of known elevation: BM
TBM
Turning Point (TP)

20. 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.

21. Leveling Terms Height of Instrument (HI)
Height (elevation) of the level’s line of sight.
HI = BS + Known Elevation

22. Determining HI HI = 100.00 ft + 4.35 ft = 104.35 ft 4.35
HI = Elev + BS
BM-1
Elev = ft.

23. Leveling Terms Foresight (FS)
Rod reading taken on a point of unknown elevation
HI – FS = Elev

24. Determining Elevation
HI = ft
6.35
Elev = HI - FS
Elev = ft. – 6.35 ft. = ft.

25. Leveling Terms Elevation (ELEV)
Vertical distance above “mean sea level” of a point on the earth’s surface.
Depending on purpose of survey, may be determined to nearest:
.1 –ft
.01 – ft.
.001 –ft.

26. Differential Leveling Field Notes
STA BS HI FS
ELEV
Dist.

27. Differential Leveling
3.21
TBM-1
BM-1
Elev = ft.

28. Differential Leveling
3.01
TBM-1
BM-1
TP-1

29. Differential Leveling
6.04
TBM-1
BM-1
TP-1

30. Differential Leveling
0.28
TBM-1
BM-1

31. Differential Leveling
6.45
TBM-1
BM-1

32. Differential Leveling
10.98
TBM-1
BM-1
TP-2

33. Differential Leveling
3.95
TBM-1
BM-1
TP-2

34. Differential Leveling
5.36
TBM-1
BM-1
TP-2

35. 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?”

36. Error Check Mathematical Error Check Allowable Error Check
Error of closure = |SBS - SFS|
Allowable Error Check
Depends on purpose of the survey
Maximum feet of error based on distance
AE = 0.10 √ M

37. Profile Leveling Field Notes
STA BS HI FS
ELEV

38. Simulated Profile Survey
TBM-A
(Elev = )

39. STA. 0+00

40. STA. 1+00

41. STA. 1+35

42. STA. 2+00

43. STA. 2+00

44. STA. 2+75

45. STA. 2+95

46. STA. 2+95