An imaginary line on the surface of the earth having a constant inclination with the horizontal (slope) is called contour gradient. The inclination of a contour gradient is generally given either as rising gradient or falling gradient, and is expressed as ratio of the vertical height to a specified horizontal distance. If the inclination of a contour gradient is 1 in 50, it means that for every 50 m horizontal distance, there is a rise (or fall) of 1 m.

When the inclination of a contour gradient is given its direction from a point may be easily located either on the map or on the ground by the methods discussed below.

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