The Geodetic Datum of Australia (GDA94) and the World Geodetic System (WGS84) are two separate coordinate reference systems used to represent locations on Earth. Both datums use a latitude-longitude coordinate system, but they differ in their choice of the prime meridian and grid spacing. This article compares and contrasts GDA94 and WGS84, highlighting the key differences between them.
What is GDA94?
GDA94 is a geodetic datum that was introduced in Australia in 1994. It superseded the earlier Australian Geodetic Datum (AGD66) and provides a more accurate representation of the size and shape of the Australian continent. GDA94 is based on the GRS80 ellipsoid and is closely aligned with the World Geodetic System 1984 (WGS84). As such, it provides a good basis for GPS positioning. GDA94 is also used by many online mapping services, such as Google Maps and Bing Maps.
What is WGS84?
- WGS84 is a geographic coordinate system that is used by GPS devices to pinpoint locations on the Earth’s surface. The system was first developed in 1984 by the United States Department of Defense, and it has since been adopted as the standard by most GPS manufacturers.
- WGS84 is based on an ellipsoidal model of the Earth, which more closely approximate its true shape than the traditional sphere-based model. This allows for more accurate positioning, particularly at high latitudes.
- In addition, WGS84 includes a number of other improvements, such as a refined prime meridian and a more precise definition of the Earth’s circumference. As a result, WGS84 is the most widely used coordinate system for GPS applications.
Differences between GDA94 and WGS84
- GDA94 (Geocentric Datum of Australia 1994) and WGS84 (World Geodetic System 1984) are two different geodetic datums. GDA94 is a geocentric datum that is specific to Australia, while WGS84 is a global datum.
- GDA94 is based on the GRS80 (Geodetic Reference System 1980) ellipsoid, while WGS84 is based on the WGS72 (World Geodetic System 1972) ellipsoid. GDA94 has a slightly different origin than WGS84, and as a result, there is a small difference in the coordinates of points between the two datums.
- In addition, GDA94 uses the Australian Map Grid (AMG) as its primary coordinate system, while WGS84 uses the World Geodetic System (WGS). GDA94 is more accurate in Australia than WGS84, but outside of Australia, WGS84 is more accurate. For this reason, GDA94 is generally considered to be more appropriate for use in Australia, while WGS84 is more appropriate for use outside of Australia.
Conclusion
The differences between GDA94 and WGS84 are important to understand for anyone working with spatial data. The difference in latitude and longitude can cause problems when trying to compare or overlay data sets from different sources. If you are working with spatial data, it is important to be aware of the difference between these two coordinate systems and to use the correct one for your project.
