1. LEVELLING
AND
CONTOURING
BY:- ANAND R. JIBHAKATE
CIVIL ENGINEER 1 1

2. LEVELLING LEVELLING 2 LEVELLING
According to science
Leveling is a branch of surveying which deals with the measurement of relative heights of different points on, above or below the surface of the earth. Thus in leveling, the measurements (elevations) are taken in the vertical plane.
Simple Definition
Leveling is the process used to determine a difference in elevation between two points.
LEVELLING 2

3. Definitions LEVELLING 3 DEFINITIONS
Station:- A point where the levelling staff is kept.
Height of instrument:- It is the elevation of the plane of sight with respect to assumed datum. It is also known as plane of collimation.
Datum line ( M.S.L. ) :- Is the level (line) which are attributed to it points levels on the surface of the Earth. Which is the average sea level.
Reduced level ( R.L) :- Is the high point from datum line.
Benchmark (B .M ) :- Are fixed points information site and attributed placed in different places until you start racing them when conducting settlement .
Back sight ( B.S.) :- Is the first reading taken after placing the device in any position so that we see the greatest possible number of points required to find the elevation .
LEVELLING 3

4. DEFINITIONS
BENCHMARKS
LEVELLING 4

5. LEVELLING 5 DEFINITIONS
Fore sight (F.S) :- Is the last reading taken before the transfer device.
Change point(CP) or turning point(TP): The point at which both BS and FS are taken.
Intermediate sight ( I.S.) :- Is reading taken between the back sight and fore sight reading .
Elevation of line of sight ( H.I) :- Is the imaginary vertical level determined by the line of sight to the amount of increase or decrease for sea level .
LEVELLING 5

6. LEVELLING 6 DEFINITIONS
Tripod stand :- is a portable three-legged frame, used as a platform for supporting the weight and maintaining the stability of some other object.
TRIPOD STAND
PLUMB BOB
TRIPOD STAND
LEVELLING 6

7. 7

8. LEVELLING 8 DEFINITIONS
Leveling Staff :-Is a wooden or metal ruler one side runway to meters and centimeters. And is a ruler of solid wood 2 , 3 , 4 , 5 meters in length and usually 4 meters .
LEVELLING 8

9. LEVELING OF THE INSTRUMENT
Leveling of the instrument is done to make the vertical axis of the instrument truly vertical. It is achieved by carrying out the following steps:
Step 1: The level tube is brought parallel to any two of the foot screws, by rotating the upper part of the instrument.
Step 2: The bubble is brought to the centre of the level tube by rotating both the foot screws either inward or outward. (The bubble moves in the same direction as the left thumb.)
Step 3: The level tube is then brought over the third foot screw again by rotating the upper part of the instrument.
Step 4: The bubble is then again brought to the centre of the level tube by rotating the third foot screw either inward or outward.
LEVELLING 9

10. LEVELING OF THE INSTRUMENT
Step 5: By rotating the upper part of the instrument through 180 ° , the level tube is brought parallel to first two foot screws in reverse order. The bubble will remain in the centre if the instrument is in permanent adjustment.
LEVELLING 10

11. LEVELLING 11 TYPES OF LEVELLING TYPES OF LEVELLING 1] Simple levelling
2] Differential levelling
3] Fly levelling
4] Profile levelling
5] Cross sectional levelling
6] Reciprocal levelling
There are two methods for obtaining the elevations at different points:
1] Height of instrument (or plane of collimation) method
2] Rise and fall method
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12. LEVELLING Simple levelling:- 12 TYPES OF LEVELLING
When the difference in the elevation of two nearby points is required then simple levelling is performed.
LEVELLING 12

13. Differential levelling:-
TYPES OF LEVELLING
Differential levelling:-
Performed when the final point is very far from the final point.
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14. LEVELLING Fly levelling 14 TYPES OF LEVELLING
Performed when the work site is very far away from the bench mark.
The surveyor starts by taking BS at BM and proceed towards worksite till he finds a suitable place for temporary BM. All works are done with respect to temporary BM.
At the end of the day the surveyor comes back to original BM.
This is called fly levelling.
LEVELLING 14

15. LEVELLING Profile levelling:- 15 TYPES OF LEVELLING
Profile levelling, which yields elevations at definite points along a reference line, provides the needed data for designing facilities such as highways, railroads, transmission lines.
Reduced levels at various points at regular interval along the line is calculated.
After getting the RL of various points the profile is drawn. Normally vertical scale is much larger than horizontal scale for the clear view of the profile.
LEVELLING 15

16. Reciprocal levelling:-
TYPES OF LEVELLING
Reciprocal levelling:-
When levelling across river is required then this method is applied to get rid of various errors.
LEVELLING 16 16

17. METHODS LEVELLING 17 METHODS OF LEVELLING
1] Height of Instrument method
The basic equations are
Height of instrument for the first setting= RL of BM + BS(at BM)
Subtract the IS and FS from HI to get RL of intermediate stations and change points.
Checking: ΣBS -ΣFS = Last RL –First RL. This is –ve for FALL and +ve for RISE.
LEVELLING 17

18. 18

19. METHODS LEVELLING 19 METHODS OF LEVELLING 2] Rise and Fall method
In this method the difference of the present staff reading is subtracted from the previous staff reading.
Previous reading –present staff reading = +ve, denotes RISE
Previous reading –present staff reading = -ve, denotes FALL
Checking: ΣBS -ΣFS = Last RL –First RL= ΣRise -ΣFall
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20. 20

21. CONCEPT
FIND THE DIFFERENT BETWEEN BENCH MARK AND TOP OF SLOPE
Rotate dumpy round
Rotate dumpy round
Fore sight
1 m
Back sight
6 m
TOP OF SLOPE ?
Back sight
9 m
Fore sight
2 m
BENCH MARK ELEVATED
e.g. 100m
Divide hill into 3 spots to make easier
Otherwise too far to see or level staff not long enough
Move level staff to new spot
Move dumpy level to new spot
Move level staff to new spot
LEVELLING 21 21

22. CONCEPT 112-100=12M SO THE DIFFERENCE IN HEIGHT IS Ground level
Level of dumpy=113m
Fore sight
1 m 6m 1m
Level of dumpy=109m
Back sight
6 m
6m+107m
Fore sight
2 m 9m 2m
Back sight
9 m
100m+9m
SO THE DIFFERENCE IN HEIGHT IS
=12M
BENCH MARK ELEVATED
e.g. 100m
Ground level
Back sight
[from dumpy level]
Height of instrument [ground level+ back sight from dumpy level]
Fore sight [from dumpy level]
Height of new point [height of instrument fore sight]
Bench mark
100 9
109 2
107 6
113 1
112 22

23. CONTOURING 23

24. CONTOURS 24 CONTOURS Contours are those lines you can see on OS maps.
Area that is flatter with only a gentle slope
Contours are those lines you can see on OS maps.
A contour line is an imaginary line that joins points of equal height above sea level.
They can be used to learn about the shape of the land (the relief).
A map with only a few contour lines will be flat (and often low lying)
If a map has lots of contours it is a mountainous or hilly area.
The actual pattern of the lines will tell you more detail about the area too.
Steep slopes
CONTOURS 24

25. CONTOURS CONTOURS 25 CONTOURS
Contour An imaginary line on the ground surface joining the points of equal elevation is known as contour.
In other words, contour is a line in which the ground surface is intersected by a level surface obtained by joining points of equal elevation. This line on the map represents a contour and is called contour line.
Contour Map :-A map showing contour lines is known as Contour map.
A contour map gives an idea of the altitudes of the surface features as well as their relative positions in plan serves the purpose of both, a plan and a section.
CONTOURS 25

26. Contouring CONTOURS 26 PURPOSE OF CONTOURING CONTOURING
The process of tracing contour lines on the surface of the earth is called Contouring.
PURPOSE OF CONTOURING
Contour survey is carried out at the starting of any engineering project such as a road, a railway, a canal, a dam, a building etc.
i) For preparing contour maps in order to select the most economical or suitable site.
ii) To locate the alignment of a canal so that it should follow a ridge line.
iii) To mark the alignment of roads and railways so that the quantity of earthwork both in cutting and filling should be minimum.
CONTOURS 26

27. CONTOURING
iv) For getting information about the ground whether it is flat, undulating or mountainous.
v) To find the capacity of a reservoir and volume of earthwork especially in a mountainous region.
vi) To trace out the given grade of a particular route.
vii) To locate the physical features of the ground such as a pond depression, hill, steep or small slopes.
CONTOURS 27

28. METHODS OF CONTOURING CONTOURS (1)Direct Method and 28
There are mainly two methods of locating contours:-
(1)Direct Method and
(2) Indirect Method.
CONTOURS 28

29. 1] Direct Method: CONTOURS 29 METHODS OF CONTOURING DIRECT METHOD
In this method, the contours to be located are directly traced out in the field by locating and marking a number of points on each contour.
These points are then surveyed and plotted on plan and the contours drawn through them.
This method is most accurate but very slow and tedious as a lot of time is wasted in searching points of the same elevation for a contour.
This is suitable for small area and where great accuracy is required
DIRECT METHOD OF CONTOURING 50 48
B.M. 46
CONTOURS 29

30. Procedure: CONTOURS 30 METHODS OF CONTOURING DIRECT METHOD
To start with, a temporary B.M is established near the area to be surveyed with reference to a permanent B.M by fly levelling.
The level is then set up in such a position so that the maximum number of points can be commanded from the instrument station.
The height of instrument is determined by taking a back sight on the B.M. and adding it to the R.L. of bench mark.
The staff reading required to fix points on the various contours is determined by subtracting the R.L. of each of the contours from the height of instrument.
CONTOURS 30

31. CONTOURS Example: 31 METHODS OF CONTOURING DIRECT METHOD
If the height of instrument is 82.48m., then the staff readings required to locate 82, 81 and 80m contours are 0.48, 1.48 and m respectively. The staff is held on an approximate position of point and then moved up and down the slope until the desired reading is obtained. The point is marked with a peg.
Similarly various other points are marked on each contour. The line joining all these points give the required contour. It may be noted that one contour is located at a time. Having fixed the contours within the range of the instrument, the level is shifted and set up in a new position.
CONTOURS 31

32. Procedure (Contd…..) CONTOURS 32 METHODS OF CONTOURING DIRECT METHOD
The new height of instrument and the required staff readings are then calculated in a similar manner and the process repeated till all the contours are located.
The positions of the contour points are located suitably either simultaneous with levelling or afterwards.
A theodolite , a compass or a plane table traversing is usually adopted for locating these points.
The points are then plotted on the plan and the contours drawn by joining the corresponding points by dotted curved lines.
CONTOURS 32

33. Direct Method By Radial Lines
METHODS OF CONTOURING
DIRECT METHOD
Direct Method By Radial Lines
RADIAL LINES METHOD OF CONTOURING 70 65 60 55
This method is suitable for small areas, where a single point in the centre can command the whole area. Radial lines are laid out from the common centre by theodolite or compass and their positions are fixed up by horizontal angles and bearings.
CONTOURS 33 33

34. Direct Method By Radial Lines (contd.):
METHODS OF CONTOURING
DIRECT METHOD
Direct Method By Radial Lines (contd.):
Temporary bench marks are first established at the centre and near the ends of the radial lines .
The contour points are then located and marked on these lines and their positions are determined by measuring their distances along the radial lines.
They are then plotted on the plan and the contours drawn by joining all the corresponding points with the help of a plane table instrument.
CONTOURS 34

35. 2. INDIRECT METHOD CONTOURS 35 METHODS OF CONTOURING INDIRECT METHOD
In this method the points located and surveyed are not necessarily on the contour lines but the spot levels are taken along the series of lines laid out over the area .
The spot levels of the several representative points representing hills, depressions, ridge and valley lines and the changes in the slope all over the area to be contoured are also observed.
Their positions are then plotted on the plan and the contours drawn by interpolation.
This method of contouring is also known as contouring by spot levels.
CONTOURS 35

36. CONTOURS 36 METHODS OF CONTOURING INDIRECT METHOD
This method is commonly employed in all kinds of surveys as this is cheaper, quicker and less tedious as compared to direct method. There are mainly three method of contouring in indirect method:
(I) BY SQUARES [SQUARE METHOD]:-
In this method, the whole area is divided into number of squares, the side of which may vary from 5m to 30m depending upon the nature of the ground and the contour interval. The square need not be of the same size throughout.
The corners of the squares are pegged out and the reduced levels of these points are determined with a level.
CONTOURS 36

37. METHODS OF CONTOURING
INDIRECT METHOD
SQUARE METHOD
CONTOURS 37

38. CONTOURS 38 METHODS OF CONTOURING INDIRECT METHOD
(II) By Cross- Sections:
This method is most suitable for the survey of long narrow strips such as a road, railway or canal etc.
CONTOURS 38

39. CONTOURS 39 METHODS OF CONTOURING INDIRECT METHOD
(III) By Tacheometric method:
A techeometer is a transit theodolite having a diaphragm fitted with two stadia wires, one above and other below the central wire.
The horizontal distance between the instrument and staff station may be determined by multiplying the difference of the staff readings of the upper and lower stadia wires with the stadia constant of the instrument, which is usually 100.
Thus the techeometer is used for both the vertical as well as horizontal measurements.
Stadia Wires at Diaphragm
CONTOURS 39

40. iii) By Tacheometric method (contd…):
METHODS OF CONTOURING
INDIRECT METHOD
iii) By Tacheometric method (contd…):
This method is most suitable in hilly areas as the number of stations which can be commanded by a techeometer is far more than those by a level and thus the number of instrument settings are considerably reduced. A number of radial lines are laid out at a known angular interval and representative points are marked by pegs along these radial lines. Their elevations and distances are then calculated and plotted on the plan and the contour lines are then interpolated.
CONTOURS 40

41. BY:- ANAND R. JIBHKATE CIVIL ENGINEER
THANK YOU
BY:- ANAND R. JIBHKATE
CIVIL ENGINEER 41