The accuracy with which reference systems and Earth orientation data can be defined is limited by the systematic errors which arise in the treatment of astronomical and geoetic observations. Constants and models must be reevaluated and improved, if possible, as measurement precision improves. Both the astronomical and geodetic communities maintain sets of conventional standards which change slowly with time, as well as "current best estimates" for high-precision users of reference systems. The International Earth Rotation Service (IERS) Conventions are discussed from the theoretical and applied points of view. Specific constants and models are described.
展开▼
