World Geographic Reference System: Difference between revisions

Revision as of 03:48, 17 February 2015

Revision as of 03:49, 17 February 2015

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* Each of the 1-degree quadrangles is further subdivided into 60 1-minute longitude zones, numbered 00 through 59 from west to east, and 60 1-minute latitude bands, numbered 00 to 59 from south to north. These numbers are always written as two digits, with a leading zero if necessary, and the easting is always followed by the northing. Thus, 4 letters and 4 digits give the position of any 1-minute quadrangle.

* Each of the 1-minute quadrangles may be further divided into 10 or 100 smaller divisions both north-southnorth–south and east-westeast–west, permitting the identification of 0.1-minute or 0.01-minute quadrangles. The Georef coordinate for any 0.1-minute quadrangle consists of four letters and six numbers; the Georef coordinate for any 0.01-minute quadrangle consists of four letters and eight numbers.

The initial two letters of a Georef reference, designating the 15 degree quadrangle, can be omitted, if it is clear which 15 degree quadrangle the reference applies to (e.g., when working within a restricted geographical area).

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Extensions to the above notation allow the Georef system to be used to designate an area around a reference point. This is achieved by adding an area designation to a base Georef co-ordinate. The area designation can be the letter S, to specify the sides of a rectangle (separated by the letter X); or the letter R, to specify the radius of a circle. In both cases the units are nautical miles. In addition, the letter H can be added, followed by an altitude in thousands of feet.

For example, the reference GJQJ0207S6X8 designates a rectangle centered around Deal Island (GJQJ0207), running {{convert|6|nmi|km|0}} east-westeast–west and {{convert|8|nmi|km|0}} north-southnorth–south. Designation GJPJ4103R5 means a circle around Point Lookout (GJPJ4103) with a radius of {{convert|5|nmi|km|0}}. Designation GJPJ3716H17 means a height of 17,000 feet over GJPJ3716.

== See also ==

* [[Maximum elevation figure]] correlated to each Georef quadrangle on [[Visualvisual flight rules|VFR]] aviation maps

* [[Lowest_safe_altitudeLowest safe altitude#Area_Minimum_AltitudesArea minimum altitudes|Area Minimumminimum Altitudesaltitudes]] on [[Instrumentinstrument Flightflight Rulesrules|IFR]] charts

== References ==