Geocentric model and planets were holes in invisible wheels surrounding Earth; through the holes, humans could see concealed fire. About the same time, Pythagoras thought that the Earth was a sphere (in accordance with observations of eclipses), but not at the center; they believed that it was in motion around an unseen fire. Later these views were combined, so most educated Greeks from the 4th century BC on thought that the Earth was a sphere at the center of the universe. In the 4th century BC, two influential Greek philosophers, Plato and his student Aristotle, wrote works based on the geocentric model.
Geocentric Datum of Australia 1994 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, maps in Australia were produced in miles using the Australian National Grid. At the same time as GDA94 was defined, a Universal Transverse Mercator coordinate system called the Map Grid of Australia 1994