GEOREF

georef

[′jē·ō‚ref] (navigation) world geographic reference system

GEOREF

A worldwide position reference system that may be applied to any map or chart graduated in latitude and longitude (with Greenwich as the prime meridian), regardless of projection. It is a method of expressing latitude and longitude in a form suitable for rapid reporting and plotting. This term is derived from the words The World Geographic Reference System. The system is based on the division of the entire earth surface into a number of quadrangles and subquadrangles. The first division is into twenty-four longitudinal zones, each 15° wide. They are lettered A to Z, omitting I and O, and begin eastward from the 180° meridian. Similarly, the earth is divided into twelve latitudinal bands, each 15° wide. They are lettered A to M, omitting I. The letters begin northward from the South Pole. Each 15° quadrangle is further subdivided into fifteen 1° longitudinal zones and 1° latitudinal bands, lettered A to Q, omitting I and O. They run east and north, respectively, from the southwest corner of the 15° quadrangle. Each of the subquadrangles is identified by means of four letters. The first two letters identify the 15° quadrangle, the third letter the 1° zone of longitude, and the fourth letter the 1° band of latitude. The 1° quadrangles are further divided into sixty longitudinal zones and sixty bands of latitude—each 1 min of arc. Any place in this 1-min quadrangle is identified by quoting four letters and four numerals. The four letters denote the 1° quadrangle: the first two numerals, denote the eastward minutes; and the remaining two numerals, the northern latitudinal position. In practice, where the risk of ambiguity with a neighboring 15° quadrangle is unlikely, the first two letters of the reference may be dropped.