NationMaster - Encyclopedia: Geodetic datum

A Geodetic Datum is an adjustment to position of origin and shape of the planet, used by cartographers and satellite navigation systems to translate positions indicated on their products to their real position on earth.

Examples of common Geodetic Datums are:

World Geodetic System 1984 (WGS84) - the datum of GPS
Ordnance Survey of Great Britain 1936 (OSGB36) - the usual datum of British nautical charts and Ordnance Survey maps until 2001

The difference between WGS84 and OSGB36 is 140 metres / 450 feet, which for most navigational purposes is an insignificant error. For other applications, such as surveying and dive site location for SCUBA divers, 140 metres is an unacceptably large error.

Results from FactBites:

World Geodetic System - Wikipedia, the free encyclopedia (1839 words)
	As a result, the elevations in the datums are referenced to the geoid, a surface that is not readily found using satellite geodesy.
	(The datums are relatively oriented with respect to different portions of the geoid by the astro-geodetic methods already described.) The sole contribution of satellite data to the development of WGS 60 was a value for the ellipsoid flattening which was obtained from the nodal motion of a satellite.
	In January 1966, a World Geodetic System Committee composed of representatives from the Army, Navy and Air Force, was charged with the responsibility of developing an improved WGS needed to satisfy mapping, charting and geodetic requirements.

More results at FactBites »

COMMENTARY

Share your thoughts, questions and commentary here

Want to know more?
Search encyclopedia, statistics and forums:

Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 0825, t