Read land elevation maps by noting the shape and elevation levels of the contour lines drawn on them. Begin by determining the vertical distance between adjacent lines. This varies from one map to another, but remains consistent within any given map.
On most topographic maps, every fifth line is drawn more thickly and is referred to as an index line. Index lines are labeled according to height in relation to sea level. The elevation difference between adjacent lines is called the contour interval and is usually noted within the map legend.
The thinner lines between the index contours are called intermediate contour lines. Find the elevation of a given point by starting from an index line and adding or subtracting multiples of the contour interval depending on the number of intermediate lines between the index line and the destination point.
Since each line traces a given elevation around the geographic terrain, most lines close back into themselves to form concentric circles. Lines that are far apart indicate greater horizontal distance between their designated levels. This means the slope of the terrain in such areas is gradual.
Lines that are close together convey less horizontal distance from one level to the next, meaning the slope of the terrain is steeper. Lines that practically touching or join to form a single line designates an extremely vertical slope or possibly a bluff or plateau.