WHAT IS CONTOUR, ITS CHARACTERISTICS AND METHODS, USES OF CONTOUR MAPS

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WHAT IS CONTOUR :

It is an Imaginary line on the ground, joining the points of same elevation or Reduced Level is called as contour.

WHAT IS CONTOUR LINE :

A line passing through points of equal elevation or equal RL is called as contour line.

CONTOUR INTERVAL :

The Vertical distance between any two consecutive contours is called as contour interval.

HORIZONTAL EQUIVALENT :

The horizontal distance between two points on two consecutive contours is known as the horizontal equivalent.

CHARACTERISTICS OF CONTOURS :

1) Two contour lines of different elevation cannot cross each other. except in case of overhanging cliff.

2) - Contour lines closed together indicates steep slope, fig (a)

- If they are far apart they indicate gentle slope, fig (b)

- If they equally spaced then it indicate uniform slope, fig (c)

- A series of straight, parallel, & equally spaced contours represent a plane surface, fig (d)

3) A series of closed contour lines with higher value inside indicates a hill

4) A series of closed contour lines with lower value inside the loop always indicate depression or pond, valley.

5) contours line cross a ridge line or watershed line at right angle and form a 'U' shape contour.

6) Contour lines cross a valley line at right angle and form 'V' shape contour.

7) All points on a contour lines have equal elevation.

METHODS OF LOCATING CONTOURS :

Following are the different methods to locate contours.

1) Direct Method

i) By spot level

ii) By radial lines

2) Indirect Method

i) Square Method (Block contouring)

ii) Method of Cross-section

iii) Tachometric Method

iv) Plane table Method

DIRECT METHOD :

Here the contours to be plotted is actually traced on the ground by locating the points of that elevation.

INDIRECT METHOD :

Here the spot levels are taken at some selected points called as guide points and the levels of the points are determined. The contours are then drawn from the interpolation from the levels of the guide points.

USES OF CONTOUR MAP :

1) To Draw Longitudibnal section and Plan of given map.

2) To determine nature of ground in proposed area.

3) To calculate reservoir capacity.

4) For measurement of Drainage area.

5) To determine inter-visibility between two points.

6) To find intersection of surfaces and measurement of earth work.

WHAT IS CONTOUR | CHARACTERSTICS AND METHODS | CIVIL ENGINEERING | MINING ENGINEERING | MINING WORLD