A means of identifying an approximate area on the surface of the Earth by relating it to information appearing on a map, generally the graticule or grid; in military field reports, Universal Transverse Mercator (UTM) grid system is often used, combining the transverse Mercator projection with a series of zones designated for different parts of the Earth's surface; the approximate location being given by the grid zone (eg 31), the area designator and the grid reference.