A contour line is an imaginary line which connects points of equal elevation. Such lines are drawn on the plan of an area after establishing reduced levels of several points in the area. The contour lines in an area are drawn keeping difference in elevation of between two consecutive lines constant.
Characteristics of Contours
The principal characteristics of contour lines which help in plotting or reading a contour map are as follows:
Contour lines must close, not necessarily in the limits of the plan.
The horizontal distance between any two contour lines indicates the amount of slope and varies inversely on the amount of slope.