| environ. | co-ordinate system A reference system used to measure horizontal and vertical distances on a planimetric map. A coordinate system is usually defined by a map projection, a spheroid of reference, a datum, one or more standard parallels, a central meridian, and possible shifts in the x- and y-directions to locate x, y positions of point, line, and area features. A common coordinate system is used to spatially register geographic data for the same area | système de coordonnées |