Topography is the science that studies the set of principles and procedures that have the purpose of graphically displaying the Earth's surface, with its forms and details, both natural and aftificial. From the Greek topo-, place, and graphia, writing.
Countour line analysis on Map E32 (audio in spanish)
An contour line joins points of equal elevation in a map, so that when used in topographical maps, they can show hills, valleys, and slopes.
The principle of contour lines: In geodesy, is each one of the elevation contours which materializes a horizontal section of the represented relief. The equidistance, altitude difference between two succesive curves, is constant and its value depends on the scale of the map and the importance of the relief.