GeodeticDatum.Wgs84 Property
A predefined global datum used in GPS positioning.
Syntax
public static GeodeticDatum Wgs84 { get; }Property Value
The geodetic datum Wgs84 that is used in GPS positioning.
Remarks
Returns Wgs84, which represents the World Geodetic System 1984, a global geodetic datum realized by the GPS satellites and controlled by the US Department of Defense. The Wgs84 datum nowadays differs by at most a few centimeters from ITRS, the International Terrestrial Reference System, which is controlled by international civilian authorities. In some texts, you can find realizations of ITRS that have names beginning with ITRF (International Terrestrial Reference Frame), for example, "ITRF96 at epoch 1998.00". For most applications, each ITRF realization can be regarded as equivalent to Wgs84.
Wgs84 is not attached to a particular continent, but maintained so that the average drift of all continents, relative to Wgs84, becomes zero. Therefore, a position that is fixed on the ground will have Wgs84 coordinates that vary slightly over time due to continental drift: about 2.5 cm/year in Europe. This makes Wgs84 impractical for detailed mapping, and various ground-based geodetic datums have been constructed. For example, Europe has defined the ETRS89 (European Terrestrial Reference System 1989), which can be regarded as a snapshot of Wgs84 as it was on January 1, 1989, but fixed to the European ground. You can imagine that all surveyors of Europe went out that day and painted the Wgs84 graticule on the ground with permanent ink. For most applications, ETRS89 and similar datums (NAD83 in North America, GDA in Australia, etc.) can be regarded as equivalent to Wgs84, although the true difference can be up to about a meter.
Platforms
Windows, Linux, Android