What is Contouring? Methods, Maps and Uses of Contours in Surveying

What is Contouring? Methods, Maps and Uses of Contours in Surveying?

or,

Define and explain contour, contour interval, necessity of contour plotting. Discuss factors affecting the choice of contour interval ?

Solution:-

Contour

 A contour is a line joining pints of equal elevation on the ground. All the point lying on a contour will have equal elevation. e.g. A contour of 60.00m indicates that all points lying on this contour are having an elevation of 60m.

Contour interval

It is the difference of elevations between two successive contours.

Necessity of contour plotting Contours :

 Plotting of contours gives the topography of the area surveyed. It gives a general idea about the topographic features of the ground which is helpful n deciding the location or alignment of an infrastructure project.

Factors affecting the choice of contour interval :

The following factors govern the choice of contour interval :

1. Purpose of map :- The contour interval should be so selected that it serves the purpose of map. Too large contour interval may omit the necessary details of the map while a too small contour interval will add to the cost of the project.


2. Nature of ground :- The contour interval depends on the nature of ground. For a flat ground, a large contour interval may serve the purpose but for mountainous terrain, a small contour interval is required.


3. Scale of the map :- If the scale of the map is small, contour interval is kept large to avoid over-crowding of contours. However, if the map scale is large then contour interval is kept small.


4. Extent of survey :- Contour interval largely depends on the extent of survey. For surveying a large area, a large contour interval is required but for a small area of survey, contour interval may be kept small.


5. Availability of time and funds :-
 Too small contour interval will increase the survey work and thereby cost of the project. However, large contour interval will reduce the amount of time and cost

Some Important Questions About Contour 

1) What does on contour mean?

A contour is a line joining pints of equal elevation on the ground. All the point lying on a contour will have equal elevation

2) What is a contour in surveying?

In surveying Contouring is the determination of elevation of various points on the ground and fixing these points of same horizontal positions in the contour map.

3) What is direct method of contouring?

In the direct method of contouring, the R.L (Reduced Level) of various selected points on a contour line are obtained and their positions are located. The contours are then drawn by joining these points. It is a very accurate method but it is slow and tedious.

4) What are the methods of contouring?

There are two methods of contour surveying 
1) Direct method.
2) Indirect method

5)Where are contours used?

Contour lines are used to signify a 3D (three-dimensional image) of a flat surfaces. 
They are commonly used on topographic maps. Here contour lines connect continuous points of equal elevation. There is a connection between the change of height and the relative change of distance

6) What is purpose of contouring?

A contour is a line joining pints of equal elevation on the ground so

contour lines connect continuous points of equal elevation. There is a connection between the change of height and the relative change of distance.

this is the main purpose of contouring.