A map is a two-dimensional model of the earth s surface. Topographic maps are contour maps showing the elevation of the land surfaces. On a topographic map sea level is an elevation of 0 feet or 0 meters. Contour lines are isolines showing elevation. D. Reading a Topographic Map 1.
Contour lines bend towards a stream.
Contour line become smaller as elevation increases up a hill. On most maps every 4th or 5th line is an index line that is labeled. Depressions are marked by contour lines with hachures- little hairs on the contour line. BM- benchmark, a spot marked X with an exact value. Horizontal distances are measured with a ruler and compared to the map scale.