Contours and Contour Interpretation

Understanding contours and being able to interpret the shapes they make on a map is a very powerful navigational tool.

However, all too often contour interpretation is overlooked in favour of more obvious features such as streams and forests. An experienced and competent navigator will look at the contours early in the process and use the information they provide to make good navigation decisions.

What are Contours?

A map is a 2-dimensional representation of the 3-dimensional world. To be able to depict three dimensions on the flat surface of a map the cartographers employ a number of techniques. The most useful of these is using contour lines.

A contour line joins points of equal height, if you walked around a hill side at exactly 200 metres above sea level and placed a flag every few metres the line joining these flags together would be the 200 metre contour line. It would snake around the hill, in and out of the small valleys and around knolls, always staying at 200m above sea level, creating an imaginary line on the landscape. It is this line that the cartographers put on the map.

To give shape and meaning to the contour lines they are drawn every few metres apart. On most maps they are drawn at 10 metre vertical intervals, but they might be 5, 10, 15 or even 20 metre intervals, depending on the scale of the map and the level of detail provided.

Contour intervals on two different maps