Map Terminology
Bearing
The horizontal angle at a given point, measured clockwise from magnetic north or true north to a second point.
Classified roads
Roads for which surface type, width and use are identified.
Contour lines
Lines on the map connecting points of equal elevation above mean sea level; using contour lines, relief features can be profiled into a three-dimensional perspective.
Elevation
Vertical distance from a datum (usually mean sea level) to a point or object on the earth's surface.
Horizontal datum
The positional reference or basis for the geographic location of features on a map.
Magnetic declination
The angle between magnetic north and true north, expressed in degrees and minutes, east or west from true north.
Magnetic north
Direction to which a compass needle points.
Mean sea level
The average height of the surface of the sea for all stages of tide, used as a reference surface from which elevations are measured.
Projection
Geometric representation of the curved surface of the earth on a flat sheet of paper.
Relief
The physical configuration of the earth's surface, depicted on a topographic map by contour lines and spot heights.
Spot elevation
A point on a map where height above mean sea level is noted, usually by a dot and elevation value; it is shown wherever practical (road intersections, summits, lakes, large flat areas and depressions).
Surveying
The operation of taking observations or measurements to determine geographic location.
Topography
Surface features both natural and cultural, collectively depicted on topographic maps.
True north
Direction of the northern rotational axis of the earth - the North Pole.
Unclassified roads
Roads for which the surface is unidentified.
Universal Transverse Mercator (UTM) grid
A square grid system based on the Transverse Mercator projection, depicted on maps. It can be used to accurately locate the position of features on the map by distance or direction.
Vertical datum
The reference or basis for elevations (usually mean sea level).
