1. Surveying With Construction Applications, 7th Edition
Chapter 2 Leveling

2. General Terms
Elevation: a vertical distance above or below a reference datum (MSL)
Vertical line : a line from surface of the earth to the earth center.
Level line : a line in a level surface. A level surface is curved surface parallel to the mean surface of the earth.
Horizontal line : a straight line perpendicular to a vertical line
Mean sea level: The reference datum that is universally employed.
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

3. Leveling Standards and Specifications
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

4. Leveling Concepts
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

5. Leveling Process Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

6. Effects of Curvature and Refraction
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

7. Effects of Curvature and Refraction
In fact , the divergence between a level line and horizontal line is quite small . For example , over a distance 1000 ft , the divergence is ft and for 100 m the divergence is m.
All sight lines are refracted downward by the earth’s atmosphere.
Refraction is generally considered to be about one –seventh of the curvature error.
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

8. C= KA2 /2R+C c= KA2 /2R c= KA2 /2*6370 =0.0000785 kA2 km= 0.0785 kA2 m
(R+c)2= R2+ KA2
R2+2Rc+c2= R2+ KA2
c(2R+c) = KA2
C= KA2 /2R+C c= KA2 /2R c= KA2 /2*6370
= kA2 km= kA2 m
If r= 0.14c , then c+ r= K2
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

9. Types of Surveying Levels
Automatic
Digital
Tilting
Dumpy (see Appendix G)
Rotary Laser (see Part II)
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

10. Equipment: Level Instrument
Automated Levels
Easy to use (not power!)
Needs experience
Digital Levels
Push-button technique
No reading errors, special staff
Readings are stored and analyzed digitally
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

11. Tilting level: very precise leveling can be achieved using the tilting screw; however, needs to be leveled before each important rod reading, which is very time consuming, thus it is rarely used
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

12. Leveling Rods:
foot rods can be read to 0.01 ft and metric rods usually only to 0.01 m
are made from wood, metal or fiberglass and are graduated in feet or meters
most leveling surveys use two- or three-piece rods, which either fold, slide or fit together telescopically for heights of 3, 5, and 7 m, from a stored height of 1.5 m
rods are graduated in a wide variety of markings and are plumbed by using a rod level or by waving the rod slightly so that the instrument operator can take the most precise reading
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

13. Leveling Rods Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

14. Equipment: Tripod Wooden design or aluminum
From “easy to sit” to “ops, this is high”
ODINAFRICA/GLOSS Sea Level Training Course - Oostende, Belgium Nov. 2006

15. Equipment: Bubble Keep the pole upright
Any tilt will disturb your readings
ODINAFRICA/GLOSS Sea Level Training Course - Oostende, Belgium Nov. 2006

16. Survey Markers Gives you a fixed point Should be of good quality
Should be long-term
Preferable in bedrock, settled buildings, or bridges
Do not use fences or walls
ODINAFRICA/GLOSS Sea Level Training Course - Oostende, Belgium Nov. 2006

17. Definitions
Bench Mark (BM): is a permanent point of known elevation . BM established by using precise leveling techniques ( GPS),marked by bronze disk and published by federal and municipal agencies
Temporary Bench Mark (TBM) : is a semi permanent point of known elevation . TBM can be on fire hydrant, top corner of concrete culvert head wall. TBM are available from various surveying agencies
Turning Point (TP): is a point used to transfer an elevation
Height of Instrument (HI): is the elevation of the line of sight through the level.
Backsight (BS): is the rod reading taken on a point of known elevation to establish the elevation of the instrument line of sight
Foresight (FS): is a rod reading taken on TP,BM or TBM to determine its elevation
Intermediate Sight (IS): is a rod reading taken at any other point where elevation is required
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

18. Definitions Back sight (BS) Fore sight (FS) Intermediate sight (IS)
The first reading from a new instrument stand point (i.e. take the height to the instrument)
Fore sight (FS)
The last reading from the current instrument station (i.e. give the height to a benchmark)
Intermediate sight (IS)
Any sighting that is not a back sight or fore sight
ODINAFRICA/GLOSS Sea Level Training Course - Oostende, Belgium Nov. 2006

19. Leveling Procedure – One Setup
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

20. Leveling Procedure – Multiple Setups
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

21. Leveling Field Notes for Slide 11]
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

22. Example of Profile Leveling
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

23. Field Notes for Slide 14
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

24. Cross Section Surveying
Surveying With Construction Applications, 7th Edition
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25. Cross Section Field Notes
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

26. Peg Test
The purpose of peg test is to check that the line of sight through the level is horizontal( i.e., parallel to the axes of bubble tube)
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

27. Peg Test Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

28. Trigonometric Leveling
The difference in elevation between A &B in the figure shown in next slide can be determined if the vertical angle (a) and the slope distance (s) are measured. These measurements can be taken with total station or with electronic distance measurements (EDM) /theodolite combinations
V =S sin α
Elevation at point A+hi +(or – V)- rod reading (RR)= elevation at B
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

29. Trigonometric Leveling
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

30. Level Loop Adjustments
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

31. Reciprocal Leveling
To cancel instrumental and natural errors it is advised to keep BS & FS distances roughly equal
In some situation such as river crossing ,it is not always possible to balance BS & FS distances
Reciprocal leveling technique is used
Surveying With Construction Applications, 7th Edition
Barry F. Kavanagh

32. CONTOURING FROM GRID (OR SPOT) ELEVATIONS

33. Definition
A contour line is an imaginary line that passes through points having the same elevation.*

34. Uses of Contour Map
Preparation of approximate ground profiles along suggested axes of projects.
Determining the capacity of a reservoir or a dam.
Calculation of earthworks volume.
Studying possible routes in highway and railway engineering.
Determining watershed lines for hydrological studies….etc.

35. characteristics of contour lines
Contour lines are continuous.
Contour lines are relatively parallel
Evenly spaced lines indicate an area of uniform slope.
A series of closed contours with increasing elevation indicates a hill and a series of closed contours with decreasing elevation indicates a depression
Closed contours may be identified with a +, hill, or -, depression
The height between successive contours is called the vertical interval or the contour interval, the contour interval is kept constant for a map.
The horizontal distance between the same two contours is called the horizontal equivalent.
8. Closely spaced lines indicates a steep gradient.
Widely spaced lines indicate a flatter gradient

36. . Contours are Continuous
Some contour lines may close within the map, but others will not.
In this case, they will start at a boundary line and end at a boundary line.
Contours must either close or extend from boundary to boundary.

37. Contour Spacing
Evenly spaced contours indicate an area of uniform slope.
Unevenly spaced contours indicates an area with variable slope.

38. Hills and Depressions
A series of closed contours with increasing elevation indicates a hill.
Hills may be identified with a “+” with the elevations

39. Hills and Depressions--cont.
A series of closed contours with decreasing elevation indicates a depression.
Depressions may be identified with a “-”.

40. Contour Spacing
Contours spaced close together indicate a higher % slope.
Contours spaced wider apart indicate lower % slope.

41. The Gradient between A and B = Vertical Interval / Horizontal Equivalent .5 10 15 20 25 A 25 B 20 10 15 5

42. Data Collection

43. Two Issues On Data Collection
When collecting data there are two important issues:
Ensuring sufficient data is collected to define the object.
Ensuring two types of information is gathered for each station:
Location
Elevation

44. Interpolation

45. Interpolation
Drawing contour lines to produce a topographic map requires the ability to interpolated between points.
Interpolation is required because contour lines are lines of constant elevation and the station elevations that are measured in the field seldom fall on the desired contour elevation.
Interpolating is finding the proportional distance from the grid points to the contour line elevation.

46. Interpolation
Interpolating can be done by estimation for low precision maps.
It should be done by calculation and measurement for higher precision maps.
A combination of methods can also be used, depending on the use of the map.

47. Interpolating by Estimation
Study the illustration.
Logic or intuitive reasoning would conclude that when the grid points are at 102 feet elevation and 98 feet elevation, then a contour line of 100 feet elevation would be half way in between.
Note: that a dashed line has been drawn between the two points. In topographic surveying it is assumed that the area between two measured stations is a plane.

48. Interpolating by Calculation
Proportional distance is calculated using an equation.
For the previous example this would result in:
The 100 foot contour line would be located 0.5 or half of the distance between the two stations.

49. Interpolation by Calculation &Estimation
The same equation is used for all grid distances and all contour lines.
Example: Determine the location of the 96 foot contour line for the illustration.

50. Interpolation by Calculation and Measurement
Start by selecting an contour interval and two grid points.
This example starts with the 110 foot interval.
The first step is to calculate the position of the 110 foot contour between stations A1 and A2.

51. Interpolation by Calculation and measurement--cont.
The next step is to measure and mark the position of 0.6.
Next, determine which direction the contour goes between the diagonal and the other three sides of the grid.
Mark the next points.

52. Interpolation by Calculation and measurement--cont.
The 110 foot contour line passes between B1 and B2, therefore the next station is the diagonal.
These steps are followed one grid line at a time until the contour closes, or reaches the edge of the map.

53. Interpolation by Calculation and measurement--cont.
Determining the proportion for line B1:B2.

54. Interpolation by Calculation and measurement--cont.
The grid lines and diagonals for each square are considered and the contour is extended.

55. Interpolation by Calculation and measurement--cont.
The next grid line is between B2 and C2.

56. Interpolation by Calculation and measurement--cont.
Each grid line and diagonal is considered and the contour line is extend between the appropriate points.

57. Interpolation by Calculation and measurement--cont.
When the contour points form a closed shape or have extended from one edge of the map to another, a smooth line is drawn connecting the points.
The contour lines must be labeled.