On 1 January 2020, NSW and VIC adopted GDA2020 with other states progressively adopting the new datum.Ī projected coordinate system is defined on a flat, two-dimensional surface. To address this issue, as of 15 December 2017, Australia has implemented a new datum known as the Geocentric Datum of Australia 2020 ( GDA2020). Australia’s coordinates are therefore no longer aligned with Global Navigation Satellite Systems (GNSS) such as GPS. Since the implementation of the GDA94, the Australian plate has moved approximately 1.6 m. This movement means that the latitude and longitude of points in Australia are changing. The Australian plate is moving in a north-easterly direction at a rate of about 7 cm per year. The earth’s tectonic plates are constantly moving in different directions and at different speeds. However, it is essential to note that nothing on the surface of the earth is fixed. Since 2000, all Australian states and territories have adopted the Geocentric Datum of Australia 1994 ( GDA94). The coordinates of the origin point are fixed, and all other points are calculated from it ( reference). This point is known as the origin point of the datum. A point on the surface of the spheroid is matched to a specific position on the surface of the earth. WGS84 is used for GPS, while WGS 84/Pseudo-Mercator is a variant and used by web mapping tools such as Open Street Map.Ī local datum aligns its spheroid to fit the earth’s surface in a particular area closely. The most recently developed and widely used datum is the World Geodetic System 1984 (WGS84). An earth-centred, or geocentric, datum uses the earth’s centre of mass as the origin ( reference). In the last 15 years, satellite data has provided geodesists with new measurements to define the best earth-fitting spheroid, which relates coordinates to the earth’s centre of mass. While a spheroid approximates the shape of the earth, a datum defines the position of the spheroid relative to the centre of the earth. Sydney, for example, has a latitude of 33.877° S and a longitude of 151.215° E. In a geographic coordinate system, a point is referenced by its latitude and longitude values ( reference). It includes an angular unit of measure, a prime meridian, and a datum (based on a spheroid). A Geographic Coordinate System (GCS) uses a three-dimensional spherical surface to define locations on the earth.
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