193. The line joning the points having the same elevation above the datum surface, is called a-
Contour Line: An imaginary live joining the points of the same elevation above the datum surface. Contour Surface: An imaginary line at which every point is located at the same elevation above the datum. Contour Interval: The difference in elevation between successive contour lines on a map. Contour Gradient: The ratio of the vertical height to a specified horizontal distance.