DEPARTMNT OF CIVIL ENGG FET IIUI

1. GROUPMEMBERS
UMER FAROOQ 26/FET/BSCE/F-14
MUHAMMAD MOHSIN 27/FET/BSCE/F-14
ASAD ULLAH KHAN 29/FET/BSCE/F-14
IMTIAZ ASHRAF 30/FET/BSCE/F-14

2. •Methods Of Contouring:
CONTOURING
Direct Method: In-Direct Method:

3. Direct Method:
In the direct method, the contour to be plotted is actually traced on the ground.
Points which happen to fall on a desired contour are only surveyed, plotted and
finally joined to obtain the particular contour. This method is slow and tedious and
thus used for large scale maps, small contour interval and at high degree of
precision.
Random Method:
Radial Method:
Direct method of contouring is employed using Level, Tripod Stand, Staff Rod,
Plane Table, Plaster of Paris and Measuring tape.
There are two types of Direct Method, as follow;

4. Random Method:
In this method, a benchmark is required in the project area. The level and Plane
Table is set up on any commanding position and back sight is taken on the bench
mark.

5. Let the back sight(BS) reading on the bench mark be 5 feet. If the reduced level of the
bench mark(BM) is 100 feet, the height of instrument(HI) would be 100 + 5 = 105 feet.
Formula → HI = BM + BS

6. The horizontal distance between any two consecutive contours is
known as the Horizontal Equivalent.
For a given contour interval, the horizontal equivalent depends upon the
steepness of the ground.
HORIZONTAL EQUIVALENT IS
SMALLER
Because of
STEEP SLOPE
HORIZONTAL EQUIVALENT IS
GREATER
Because of
GRADUAL SLOPE

7. Horizontal equivalent
Horizontal equivalent
STEEP SLOPE GRADUAL SLOPE

8. The vertical distance between contour lines is called
the contour interval
Depending on the accuracy required, they may be plotted at 0.1-m to 0.5-m
intervals in flat terrain and 1-m to 10-m intervals in undulating terrain. The
interval chosen depends on:
(1) The type of project involved; for
instance, contouring an airstrip
requires an extremely small contour
interval.
(2) The type of terrain, flat or
undulating
(3) The cost, for the smaller the
interval the greater the amount of
field data required, resulting in
greater expense.
Contour
Interval

9. From the known elevations of the contours and the HI, the required staff readings
to fix positions on the various contours lines(contour points) are obtained by
subtracting the elevation of each of the contours from the HI.
New Elevation = H.I – Staff Reading(F.S)
Suppose the . To locate the points on the
104’, 103’, and 102’ contours, the staff readings will be
respectively as contour interval is taken 1’.
B.M=100’, B.S=5’, and H.I = 105’
1’, 2’ and 3’
104’
104’
104’
103’
103’
103’
102’
102’

10. • The staff is held on an estimated position of a point.
• It is then moved up or down the slope until the desired reading is obtained.
• The point so determined is marked by means of a white and their position is determined by
measuring the distance from plane table using MEASURING TAPE.
15m
30m
45m
104’
103’
102’
104’
103’
1’ 2’ 3’
102’

11. Can we draw a contour of 106’ , if H.I=105’ ?
QUESTION
ANSWER:
If H.I=105’ it means that 105 is the maximum reading we can take according to this H.I.
To measure 105’ elevation point according to H.I=105’ the staff reading (F.S) will be ZERO.
B.S=5’ H.I=105’
R.L=105’
F.S = 0’
H.I=105’
R.L=106’

12. So we can't measure 106’ elevation point according to H.I=105’.
To draw a contour of 106’ we must have to change the H.I upto106’ or more than 106’.
B.S=6’
H.I=106’
From this height of instrument we can draw a contour of 106’

13. Several points are thus determined and marked on each contour.
Then the points having same elevation are joined by contour line.
Contour Line
Or
Contour
Points having same
elevation

14. Radial Method:
In this method the contours to be plotted are actually located on the ground with a level
by marking various points on the RAIDIAL LINES ( radiating from one common point,
their positions are relative with each other by measuring ANGLES between them ).
In this method, first of all radial lines are drawn (by theodolite or compass radiating and
their positions are fixed up by horizontal angles and bearings) from one common point
at an angle (Ѳ) in the project area.
RAIDIAL LINE
Angle between two
RAIDIAL LINES

15. In this method a Temporary bench mark is first established in the projected area.
The level and Plane Table is set up on any commanding position and back sight is taken
on the bench mark.
Let the back sight(BS) reading on the bench mark be 5 feet. If the reduced level of the
bench mark(BM) is 100 feet, the height of instrument(HI) would be 100 + 5 = 105 feet.
Formula → HI = BM + BS

16. From the known elevations of the contours and the HI, the required staff readings to fix
positions on the Radial Lines are obtained by subtracting the elevation of each of the
contours from the HI.
New Elevation = H.I – Staff Reading(F.S)
Suppose the . To locate the points on the 104’,
103’, and 102’ contours, the staff readings will be respectively as
contour interval is taken 1’.
B.M=100’, B.S=5’, and H.I = 105’
1’, 2’ and 3’
104’
103’
102’

17. • The staff is held on an estimated position of a point.
• It is then moved up or down the slope (along the RADIAL LINE) until the desired reading is
obtained.
• The point so determined is marked by means of a white and their position is determined by
measuring the distance from plane table using MEASURING TAPE.
104’
103’
102’
104’
103’
102’
Plane table
Auto Level
10m
20m
30m
F.S=1’ F.S=2’ F.S=3’

18. 104’
103’
102’
Several points are thus determined and marked on each contour.
Then the points having same elevation are joined by contour line.
104’ 103’
102’
104’103’
102’
104’
103’
102’