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| GDA94 | |
|---|---|
| Name | GDA94 |
| Native name | Geocentric Datum of Australia 1994 |
| Established | 1994 |
| Type | Geodetic datum |
| Region | Australia |
GDA94 is a geocentric terrestrial reference frame used for geospatial positioning across Australia. It provides a consistent coordinate system for mapping, surveying, navigation, and infrastructure projects and underpinned national datasets, cadastral records, and cadastral surveying practice. GDA94 aligned Australian coordinates with international systems to support interoperability with satellite constellations and mapping efforts.
GDA94 was promulgated to replace disparate local datums and to integrate Australian positioning with global reference frames used by Geoscience Australia, Australian Bureau of Statistics, Surveying and Spatial Sciences Institute, National Mapping Council of Australia, State Surveyors-General, and agencies supporting GPS observations. The datum defines an ellipsoid, origin, orientation, scale, and epoch tied to the International Terrestrial Reference Frame conventions in effect during the early 1990s, allowing consistent coordinates for projects such as AusAID infrastructure, CSIRO geodetic networks, and national spatial datasets used by state agencies like Landgate (Western Australia), Vicmap (Victoria), Spatial Services (NSW) (New South Wales), DataVic, and local councils.
Development involved collaboration among Geoscience Australia, state mapping authorities, university research groups (for example University of New South Wales, University of Melbourne, Australian National University), and international organizations including International Association of Geodesy, International Earth Rotation and Reference Systems Service, and contributors using observations from GNSS constellations such as GPS and GLONASS. The rollout required updates to cadastral law and surveying practice overseen by bodies like the Intergovernmental Committee on Surveying and Mapping and implementation by offices such as the Department of Infrastructure, Transport, Regional Development and Communications. Major projects using GDA94 included national mapping programs of the Australian Defence Force, environmental monitoring by the Australian Antarctic Division, and coastal studies by the Bureau of Meteorology.
GDA94 is defined by a realization of a geocentric datum with parameters tied to the ellipsoid used internationally by organizations such as International Union of Geodesy and Geophysics and referenced to an epoch consistent with early 1990s GNSS solutions. The defining conventions referenced the WGS84 realization of that era and aligned with standards from the International Astronomical Union and International Earth Rotation Service. The datum provided Cartesian (X, Y, Z) coordinates centered at the Earth's mass center and associated geodetic latitude, longitude, and ellipsoidal height values used by mapping agencies, cadastral authorities, and spatial data infrastructures like PSMA Australia.
The practical realization of GDA94 was achieved via a network of permanent GNSS stations coordinated by Geoscience Australia and state networks such as ONC and state Continuously Operating Reference Station networks including CORS installations. Coordinates for survey marks were published in cadastral registers managed by entities such as the Registrar-General (New South Wales), Land Victoria, and Department of Lands (Queensland), and employed by engineering firms, utilities like Telstra and Australian Energy Market Operator, and transport agencies including Australian Rail Track Corporation. Published coordinates used datum conventions for epoch 1994.0 and included transformations for integration with mapping products produced by organizations like Esri, Trimble, and Leica Geosystems.
GDA94 shares historical ties with WGS84 realizations current in the early 1990s and was effectively static relative to the Australian tectonic plate at epoch 1994.0, while modern GNSS-based frames account for plate motion as embodied in updates like GDA2020. Transformations and comparisons involved international frames such as ITRF realizations and services provided by IERS. Key agencies including Geoscience Australia and state mapping organizations coordinated transition paths from GDA94 to newer, plate-fixed, time-stamped frames to handle continental drift and integration with services from companies like Google and international projects like Copernicus Programme.
GDA94 underpinned national cadastral systems, built-environment projects by state departments such as Transport for NSW and Department of Transport and Main Roads (Queensland), coastal management by Department of Agriculture, Water and the Environment, resource exploration by Geoscience Australia and mining companies, and emergency services mapping for agencies like State Emergency Service units. It was required in tender specifications for major infrastructure projects (e.g., East West Link, Snowy Hydro expansions) and used by academic research at institutions like Monash University and University of Western Australia for geodesy, geophysics, and climate studies linked to satellite missions such as TOPEX/Poseidon and Jason.
Transformation methods between GDA94 and other frames involved seven-parameter Helmert transformations, grid-based shifts, and plate-motion models published by authorities such as Geoscience Australia and standards bodies like Standards Australia. Tools and software implementations were provided by vendors and projects including PROJ, GDAL, EPSG Registry, AUSPOS online services, and survey software from Trimble and Leica Geosystems. Legal and procedural guidance for conversions and re-surveying to maintain cadastral integrity was issued by state surveyor-general offices and professional bodies such as the Institution of Surveyors Australia.
Category:Geodetic datums