Land Topography Terms

Topography is the graphic delineation of maps and charts showing the gradient changes of natural and man-made features. Topography determines the position of features using the coordinate system, which includes latitude, longitude and altitude. Originating in ancient Greece, topography, from the Greek words "topos" (place) and "graphia" (writing), once translated as "local history" in classic literature. After the United States Geological Survey began national mapping in 1878, most nations adopted the term topography for detailed surveys of the land.

  1. Basic Terms

    • Elevation: the vertical distance from a point on the earth's surface to the mean sea level.

      Contour Lines: the vertical impression and gradient of the land. The thin lines follow the elevation gain outlining ground features. Contour lines closer together show a steeper slope, while contour lines further apart and equally spaced show a flatter surface.

      Relief: the physical surface layout of the earth.

      Surveying: the task of recording observations and measurements to depict a geographic area.

      Projection: the two-dimension geometric representation of the curved surface of the earth.

    Directional Terms

    • Bearing: the horizontal angle measured between a point and magnetic north or true north.

      Magnetic north: the direction a compass needle points due to the magnetic draw near the north pole, also known as the north-seeking pole.

      Magnetic declination: the degree or minutes represented by the angle between the magnetic north and true north or east/west from true north.

      True north: the geographic north pole or most north rotational axis of the earth, also known as the north pole.

    Elevation Terms

    • Horizontal datum: an origin point used as a reference for a geographic location on a map.

      Vertical datum: the base reference for elevations, usually mean sea level.

      Mean sea level: an average calculated from all stages of the tide of the height of the sea.

      Spot elevation: a reference point on a map that shows the height above sea level.

    Elevation Coloring Terms

    • Hypsometric tinting: the layering of colors over a map to represent visually the change in degree of elevation. Used to enhance elevation zones, the tinting makes it easier for readers to determine level changes. The colors selected generally represent an impression of the colors seen at the different elevations. For example white, like mountain peaks, represent the highest elevations, while dark green represents deep valleys.

      Relief shading: the natural shading of color over a map to represent a visual change in degree of elevation. Using more realistic colors and depicting contour lines, relief shading follows an intuitive pattern that highlights the shapes of the ground structures.