Permanent Tides and Geodetic Datum
CHEN Jun yong (State Bureau of Surveying and Mapping, Beijing,100830)
With the development of society economy, science and technology, the requirements for accuracy, epoch and frame of geodetic datum are higher and higher. Hence the effects on the geodetic datum from the tides, polar motion, crustal movement and post rebound should be taken into account. In the paper only the influences of permanent tides on the gravity datum, height datum, geoid and deflections of the vertical are discussed. Besides, the concept and relevant computation formulae for the effects from the non tide, mean tide and zero tide are derived.