Studies of a coalescent world geodetic system’

A study has been made of the gravity field of the earth using a combined solution from free air anomalies and satellite data. Spherical harmonics up to order 8.8 have been computed in a joint solution. Satellite data from Doppler tracking (NWL) and optical observations (SAO) were added in a combined solution with full consideration of the complete covariance matrix.-This study was based on the most complete set of gravity data so far presented (approximately 500,000). The simplest type of a world geodetic system includes only geometrical observations. Such systems have a limited geodetic application because no dynamic properties can be derived from purely geometrical observations. A geodetic system that is going to be used for ballistic applications has to incorporate a solution of the gravi-metric boundary value problem consistent with the geometrical representation. Present geodetic systems already include a number of dynamic parameters presented in the form of so-called geoids. These geoids are establishing valuable reference systems mainly in a conservative application, i.e., when geometrical measurements are reduced to an analytical reference surface (normally the international ellipsoid)