This document discusses contouring in surveying. It defines contouring as determining elevation points on the ground and mapping points of equal elevation. Contour lines connect points of the same elevation. The difference between adjacent contour lines is the contour interval. Contour lines are continuous, parallel, and form U-shapes for ridges and V-shapes for valleys. Closely spaced contours indicate steep slopes while widely spaced contours indicate gentler slopes. Hachures are used to depict hills and depressions. Data collection ensures sufficient points to define terrain features and records both location and elevation. There are direct and indirect methods for contouring - direct is most accurate but indirect is faster for hilly areas.

1. COUNTOURINGin
Survey & Levelling
PRESENTATION BY: -ANANYA SADHU -
-PRAKHAR RASTOGI
-SANJANA SINGH
-ADIT GUPTA
(B.Arch 1st year)
Submitted to:
Ar. Avitesh

2. What is contouring?
• Contouring in surveying is the determination of elevation of various points on the ground
and fixing these points of same horizontal positions in the contour map.
• To exercise vertical control leveling work is carried out and simultaneously to exercise
horizontal
control chain survey or compass survey or
plane table survey is to be carried out.
• If the theodolite is used, both horizontal
and vertical controls can be achieved from
the same instrument. Based on the
Instruments used one can classify the
contouring in different group

3. CONTOUR LINE
• An imaginary line passing through
points of equal reduced level.
• The elevation difference between
the adjacent contours is called
the contour interval.
CONTOUR INTERVAL

4. Characteristics of Contours

5. 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.

6. Contour Lines are
Parallel
• Two exceptions:
• They will meet at a vertical cliff –
• They will overlap at a cave or overhang.
• When contour lines overlap, the lower
elevation contour should be dashed for
the duration of the overlap.

7. U Shapes and Ridge
• A series of V-shapes indicates a valley
and the V’s point to higher elevation.
Valleys and Higher Elevation
• A series of U shapes indicates a
ridge. The U shapes will point to
lower elevation.

8. Contour Spacing
• Contours spaced close together indicate a
steep slope.
• Contours spaced wider apart indicate less
slope.

9. Hachures Hills and Depressions
• Hachures are short lines which are
perpendicular to the contour line.
• Used to indicate a hill or a depression.

10. Data Acquisition
• When collecting topo 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

11. METHODS OF CONTOURING
DIRECT METHOD
• Most accurate but slow and tedious.
• Expensive
• Not suitable for hilly area
• During the work calculation can be done
• Calculation cannot be checked after
contouring
INDIRECT METHOD
• Not so accurate but rapid and less tedious
• Cheaper
• Suitable for hilly areas
• Calculations are not required in field
• Calculations can be checked as and when
required