Absolute coordinates are coordinates that reference the position of an object with respect to an origin in a given coordinate system. Normally, coordinates are expressed as tuples (ordered sets of elements) using numbers, but they may also use letters, alphanumeric strings, or other designators.
In a two-dimensional Cartesian coordinate system, a point on a plane is uniquely defined by its (x,y) position with respect to the origin (0,0); the perpendicular intersection of the x and y axes. In three dimensions, a point (x,y,z) is defined in space relative to the intersection of three perpendicular axes: x, y and z.
In geographical information systems, absolute coordinates reference the position of a point or other feature on a map using a specific datum within a known coordinate system. For example, a point on the globe may be referenced by its latitude and longitude with respect to the intersection of the Equator and the Prime Meridian, designated as 0 degrees latitude and 0 degrees longitude. San Francisco, California has the absolute coordinates of 37°46′45.48″ North (of the Equator), and 122°25′9.12″ West (of the Prime Meridian) using the WGS84 geodetic reference datum. Conversely, relative coordinates give the position of a point or object with respect to an arbitrary point, such as "the third house on the left" from a given intersection.
Absolute Coordinates is a command for AutoCAD software that uses the Cartesian coordinate system to specify a position in the X, Y, and (if needed) Z axes to locate a point from the 0-X, 0-Y, and 0-Z (0,0,0) point.
- Absolute Coordinates. AutoCAD Command List. North Carolina State University, Graphic Communications Program Web site. Accessed 19 May 2010.