A geographic coordinate "transformation" is a translation among different geodetic datums. There are transformations that directly convert geodetic coordinates from one datum to another. Commonly an ellipsoidal model is part of a more encompassing geodetic datum. Hellas Planitia is the lowest lying plain below the Martian geodetic datum. Standards control accuracy, surveying credentials, monumentation of boundaries and maintenance of geodetic networks. The geocentric and geodetic longitude have the same value. One other surface is involved in geodetic measurement&colon; the geoid. The transformation between geodetic and Cartesian coordinates may be found in Geographic coordinate conversion. EGM96 from 1996 is used as the geoid reference of the World Geodetic System. They are used in geodetic and land surveying. Using seismic and geodetic data, Luzon was modeled by Galgana et al. Formulas for calculating geodetic azimuth are linked in the distance article. The MREs are a direct transformation of geodetic coordinates with no intermediate ECEF step. The standard notation for geodetic latitude is . In 1960 he participated in a geodetic and astronomical expedition in the Caucasus.