Here are a few basic terms that you need to know before beginning the "learning to 'read' a contour" process. The terms include an explanation and a pictorial example.

Once you have read this material, proceed to Step 1. If you have already started the process, so to the step where you last left off.

This is the basic symbol that you will use to determine the elevation of a feature or location. It is a brown line on a topographic map and represents a line of equal elevation. All locations that a contour lines crosses have the same elevation at that point. Contour lines basically follow the curves of Earth's natural land surface features.

Click here to see an example of a contour on a topographic map.

 

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INDEX CONTOUR LINE

A bolder/wider brown line that has the elevation value marked at various intervals as a part of the line. These contours typically occur every fifth line. Use an index contour near the point for which you are trying to find the elevation as a first step to determining the elevation of that point.

Example of an index contour

 

In addition to the basic contour line, there are two other types of contours that you will need to be able to recognize:

Supplemental Contour: A dotted or dashed line that represents half the interval between the other contour lines. Supplemental contours are used to produce a more complete picture of relief in a relatively flat area, particularly in flat areas. When supplemental contours are used, an explanatory note is placed in the marginal information.

Example of a supplemental contour

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Depression Contour: A contour that indicates a hole and is represented by a "hachured" brown line. A depression is a point inside a contour that is lower than the contour; a point outside the depression contour is higher than the contour.

Example of a depression contour