Geocentric model they also appear to revolve around Earth about once per day. The stars appeared to be fixed on a celestial sphere rotating once each day about an axis through the geographic poles of Earth. Second, Earth seems to be unmoving from the perspective of an earthbound observer; it feels solid, stable, and stationary. Ancient Greek, ancient Roman, and medieval philosophers usually combined the geocentric model with a spherical Earth, in contrast to the older flat Earth model implied in some mythology. The ancient Jewish Babylonian uranography pictured a flat Earth with a dome-shaped, rigid canopy called the firmament placed over
Geocentric Datum of Australia 1994 predicted that by 2020, the difference will be around 1.8m The Intergovernmental Committee on Surveying and Mapping (ICSM) has proposed a two-stage plan to update the datum, given a working title of GDA2020. Geocentric Datum of Australia 1994 The Geocentric Datum of Australia 1994 (GDA94) is a geodetic datum covering the Australian continent. Details of this datum are provided by the GDA94 Technical Manual. The GDA94 datum was formalized in 1994, replacing the previous datums which were being used in Australia at the time, the Australian Geodetic Datum 1966 (AGD66) and the Australian Geodetic Datum 1984 (AGD84). Prior to 1966,