Numbers in the map represent the elevation in feet above sea level. This information is known as topography, and maps which display elevation information are called topographic maps. There are lots of ways that people make use of topographic data. Scientists use information about topography to help in their studies of plants and animals. Elevation information provides clues about soil types, and can tell you how the surface of Earth changes due to the actions of glaciers, rivers, and the processes of mountain building and erosion.
City planners use topographic data to help locate suitable places for structures or recreation.
Aircraft pilots require accurate topographic information for flight planning and navigation, and the military requires precise topographic information for training and real time operations. Knowing the exact height and location of mountain peaks enables the cellular phone industry to place towers in optimal locations for signal reception. In addition, topographic maps are the mainstay of day hikers and backpackers. For various parts of the world, maps of Earth's topography are limited, inaccu rate, or nonexistent. For example, many mountain chains, inhospitable deserts, and tropical rain forests have topographic coverage that is totally inadequate mainly because of the difficulty in getting to these locations.