World Meteorological Organization (WMO) squares is a system of

geocode A geocode is a code that represents a geographic entity (location or Geographical feature, object). It is a unique identifier of the entity, to distinguish it from others in a finite set of geographic entities. In general the ''geocode'' is a ...

s that divides a

world map A world map is a map of most or all of the surface of Earth. World maps, because of their scale, must deal with the problem of projection. Maps rendered in two dimensions by necessity distort the display of the three-dimensional surface of t ...

with latitude-longitude gridlines into grid cells of 10°

latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...

by 10°

longitude Longitude (, ) is a geographic coordinate that specifies the east- west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lett ...

, each with a unique, 4-digit numeric identifier. On the

plate carrée projection The equirectangular projection (also called the equidistant cylindrical projection or la carte parallélogrammatique projection), and which includes the special case of the plate carrée projection (also called the geographic projection, lat/l ...

, the grid cells appear square; however, if the Mercator projection is used, the grid cells appear 'stretched' vertically nearer the tops and bottoms of the map. On the actual surface of the

Globe A globe is a spherical Earth, spherical Model#Physical model, model of Earth, of some other astronomical object, celestial body, or of the celestial sphere. Globes serve purposes similar to maps, but, unlike maps, they do not distort the surface ...

, the cells are approximately "square" only adjacent to the

Equator The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...

, and become progressively narrower and tapered (also with curved northern and southern boundaries) as they approach the

poles Pole or poles may refer to: People *Poles (people), another term for Polish people, from the country of Poland * Pole (surname), including a list of people with the name * Pole (musician) (Stefan Betke, born 1967), German electronic music artist ...

, and cells adjoining the poles are unique in possessing three faces rather than four. Each 10°x10° square is allocated a number between 1000 and 7817. The numbering system is based first on "global quadrant" numbers where 1=NE, 3=SE, 5=SW, 7=NW which gives the initial digit of any square code (1xxx, 3xxx, 5xxx, 7xxx). The second digit (x0xx through x8xx) indicates the number of tens of degrees latitude (north in global quadrants 1 and 7, south in global quadrants 3 and 5) of the 'minimum' square boundary (nearest to the Equator), i.e. a cell extending between 10°N and 20°N (or 10°S and 20°S) has this digit = 1, a cell extending between 20°N and 30°N has this digit = 2, etc. The third and fourth digits (xx00 through xx17) similarly indicate the number of tens of degrees of longitude of the 'minimum' square boundary, nearest to the

Prime Meridian A prime meridian is an arbitrarily chosen meridian (geography), meridian (a line of longitude) in a geographic coordinate system at which longitude is defined to be 0°. On a spheroid, a prime meridian and its anti-meridian (the 180th meridian ...

. By way of illustration, the square 1000 thus extends from 0°N to 10°N, 0°E to 10°E, and the square 7817 from 80°N to 90°N, 170°W to 180°W, adjacent to the major portion of the

International Date Line The International Date Line (IDL) is the line extending between the South and North Poles that is the boundary between one calendar day and the next. It passes through the Pacific Ocean, roughly following the 180.0° line of longitude and de ...

. In this manner, reverse-engineering (decoding) the relevant square boundaries from any particular WMO Square identifier is straightforward, in contrast to some other similar systems e.g. Marsden squares. WMO squares are also used as the basis for the

c-squares C-squares (acronym for the ''Concise Spatial QUery And REpresentation System'') is a system of spatially unique, location-based identifiers (geocodes) for areas on the surface of the earth, represented as cells from a latitude- and longitude-bas ...

system for spatial indexing, which further divides 10°x10° WMO squares into smaller units of 5°x5°, 1°x1°, 0.5°x0.5°, 0.1°x0.1°, and so on.

External links

* Example of chart at NOD
World Ocean Database 2005
{{Geocoding-systems Geocodes World Meteorological Organization

See also

External links