GDA94 and GDA2020 are geodetic datums used for referencing locations on the Earth's surface. GDA94 was developed in 1994 and widely used in Australia, while GDA2020 was introduced in 2020 as an updated and more accurate version. GDA2020 considers the movement of the Australian continent and provides better alignment with GPS and satellite measurements. The relationship between the two can be seen as an evolution or upgrade, with GDA2020 improving upon GDA94 by incorporating more precise measurements and adjustments. The transition from GDA94 to GDA2020 involves a coordinate shift, and it's important to use the correct datum for accurate measurements.