To enhance the explanation of topographic mapping, we will also discuss some additional field methods the surveyor uses. In fact, this is the main feature that makes a topographic map different from other types of maps. Before you go any further, refresh your memory on the subject of topographic relief.
Relief is the term for variance in the vertical configuration of the earth s surface.
You have seen how relief can be shown in a plotted profile or cross section. These, however, are views on a vertical plane, but a topographic map is a view on a horizontal plane. On a map of this type, relief may be indicated by the following methods. Shading is a pictorial method of showing relief by the use of light and dark areas to suggest the shadows that would be created by parallel rays of light shining across the area at a given angle. Relative steepness or flatness is suggested by varying the lengths and weights of the lines.