Contour interval
Also called: Vertical interval, VI · Topic: Topographical Maps: Relief Representation and Interpretation · NCERT: Class 11, Ch 5 "Topographical Maps"
Meaning
The contour interval (also called the vertical interval, VI) is the fixed difference in height between two contour lines that come one after another. Contours are lines joining places of equal height above mean sea level. Common intervals are 20, 50 or 100 metres. The interval is usually the same across one map, and it is printed in the marginal information. Knowing it lets you read the height of any contour and judge how steep the land is.
Example
Suppose a sheet of the Nilgiri hills in Tamil Nadu uses a 20 m interval. Then the contours rising up a slope read 100, 120, 140 m and so on.
Don't confuse with
- Horizontal equivalent (HE): this is the ground distance between two contours that come one after another. The contour interval stays fixed, but the HE changes. It is small on steep slopes and large on gentle ones.
Related concepts
- Contour line
- Horizontal equivalent
- Gentle slope
- Steep slope
- Concave slope
- Convex slope
- Undulating slope