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Abstract:
The definition of a new GRS becomes necessary because since the introduction of the current conventional system GRS80 the knowledge in geodesy has improved significantly (e.g. GNSS, gravity space missions), the IERS conventions have changed and the use of the parameters became inaccurate and inconsistent over time. The problem of the permanent Earth tide was not yet a topic at the epoch of the definition of GRS80. The acceptance of the IAG Resolution No. 1 in 2015, which defines the potential at sea level (W0), even increases the inconsistency in the geodetic parameters of the conventional GRS.The new set of parameters is based on the four fundamental parameters: W0 (potential at reference level), J2 (dynamic form factor, “flattening”), GM (geocentric gravitational constant) and ω (angular velocity of the Earth). All these quantities are well observed and monitored by various geodetic space techniques. Most of the defining parameters change with time. This includes seasonal variations and long-term trends.The calculation of a new set of parameters is one thing. The main problem is the discussion if the replacement of GRS80 as the conventional system is really a good idea. This would just lead to more confusion and to additional work without a big benefit. Many users do not see the necessity to replace it, as it is seen just as a conventional model for the conversion of geocentric coordinates or for the calculation of gravity anomalies.
