Australia: GDA94 to GDA2020 Transition Risk の座標変換

1.8メートルの地殻変動シフト

The Australian tectonic plate is one of the fastest moving on Earth, shifting north-east at approximately 7 centimeters per year. In 1994, Australia adopted GDA94 (Geocentric Datum of Australia 1994). Because GDA94 is statically fixed to the plate, it "moved" with the continent.

By 2020, the physical landmass of Australia had drifted approximately 1.5 to 1.8 meters relative to the GPS satellite constellation (WGS84). This meant a user with a smartphone or a commercial drone would see their position shifted 1.8 meters off of official GDA94 maps.

The Adoption of GDA2020

To fix the smartphone and autonomous vehicle alignment issue, Australia implemented GDA2020 (EPSG:7844). GDA2020 "jumped" the coordinate system forward to align with the expected position of the tectonic plate at the year 2020.0.

Engineering Risk & Liability

The 1.8 meter magnitude of the shift is the "danger zone". It is large enough to cause asset strikes (hitting a buried fiber optic cable) and boundary encroachments, but small enough that it is not immediately visually obvious on a GIS screen zoomed out to a city-block level.

Strict Liability: Surveyors and GIS professionals must explicitly label all data as GDA94 or GDA2020. Mixing the two without applying the official national transformation grids (NTv2) is a direct breach of the standard of care.