Time-dependent conversion between GDA94 and WGS84

The WGS84 and GDA94 datums were the same at the start of 1994, but the current difference is around one metre. GDA94 coordinates move relative to the International Terrestrial Reference Frame (ITRF) that's used for WGS84. This is done so that coordinates in GDA94 continue to map to the same points on the surface of the Australian continent even though the whole plate is moving at about 7cm per year in a NNE direction across the globe.

In AusDatumTool, we've implemented an algorithm using the time-dependent, 14-parameter shift values published by Geoscience Australia. When converting between these datums, an Epoch button is visible which allows you to enter the year and day for the conversion. This defaults to the current date.

References

GDA Technical Manual, ICSM.
GDA94, ITRF & WGS84 What’s the difference?, Richard Stanaway.

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