Profile and Differential Leveling

1. Profile and Differential Leveling AGME 1613Fundamentals 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. B Difference? A Differential Leveling Purpose is to determine the difference in elevation between two (or more) points on the Earth’s surface.

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

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

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

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

13. Reading the Leveling Rod 3

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

15. Direct Differential Leveling 3.21 B A

16. - B A 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?

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 + 00 = 0 hundred feet + 0 feet • STA 2 +75 = two hundred feet + 75 feet • STA 5 + 05 =?????????

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 = 100.00 ft.

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

24. Determining Elevation HI = 104.35 ft 6.35 Elev = HI - FS Elev = 104.35 ft. – 6.35 ft. = 98.00 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

27. Differential Leveling 3.21 TBM-1 BM-1 Elev = 1225.50 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. AE = 0.10 √ M 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

37. Profile Leveling Field Notes

38. Simulated Profile Survey (Elev = 100.00) TBM-A

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