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EPSG:4283 — GDA94

GDA94 — Australia's previous geodetic datum, retained for legacy datasets but superseded by GDA2020.

Code
EPSG:4283
Type
Geographic 2D
Area
Australia - GDA

PROJ definition

+proj=longlat +ellps=GRS80 +no_defs +type=crs

Geographic bounds

W 93.41°   S -60.55°   E 173.34°   N -8.47°

Convert coordinates with EPSG:4283

Official EPSG transformations for GDA94

Datum transformations involving EPSG:4283 published in the EPSG dataset, with parameters, accuracy and area of use:

About EPSG:4283

EPSG:4283 is the Geocentric Datum of Australia 1994 (GDA94), aligned with ITRF92 at epoch 1994.00 on the GRS 80 ellipsoid. It was Australia's official datum from 1994 to 2020 and is the reference for the legacy Map Grid of Australia 1994 zones (MGA94, EPSG:28349-28358).

Because the Australian plate moves ~7 cm/year north-east, by 2020 GDA94 had drifted ~1.8 m relative to ITRF and modern GPS-derived positions. GDA2020 (EPSG:7844) was introduced to restore alignment. GDA94 remains in widespread use in legacy datasets — historical aerial imagery, older cadastral maps, pre-2020 government data exchanges — and a published Helmert transformation (EPSG:8048) converts between the two with millimetre precision.

Common use cases

  • Reading legacy Australian government geospatial data
  • Historical surveys, cadastre and aerial imagery
  • MGA94 projected coordinates
  • Cross-checking results against pre-2020 Geoscience Australia products

Common transformations from EPSG:4283

Frequently asked questions

Is GDA94 the same as WGS 84?
They were close in 1994 but have diverged due to plate motion. Treat them as different datums for any work better than ~1 m.
What is the proj4 string for EPSG:4283?
The proj4 definition for EPSG:4283 is: +proj=longlat +ellps=GRS80 +no_defs +type=crs
Where is EPSG:4283 used?
EPSG:4283 (GDA94) is defined for the area: Australia - GDA.