World: A multipurpose GPS-network computer package

Abstract

WORLD is a multipurpose package to compute geodetic positions in geometry and gravity space. Here undifferenced GPS carrier beat phase observations are processed in the free network mode, namely by the prototype program called PUMA. Within two alternative model formulations, the classical Gauß-Markov Model and the so-called Mixed Model, simultaneously estimated / predicted parameters are those of type (i) Cartesian ground station coordinates (geodetic positioning), (ii) Cartesian satellite coordinates (orbit determination), (iii) receiver- and satellite-specific bias terms, (iv) initial epoch ambiguities and (v) proportional tropospheric corrections. The Mixed Model parameters appear from linearization as a point of stochastic prior information. Namely the weight matrices of stochastic prior information, e.g. for orbit parameters, is assumed to be known. Estimators of type BLUE and predictors of type inhom BLIP and hom BLUP are used. Chapter four discusses in all detail the real analysis of GPS satellite networks of free type. Most notable are the estimated bias terms α, β, γ, in a twofold classification model. The operability of PUMA is demonstrated by the use of multistation phase observations (Wild-Magnavox WM 101-receivers) in a local Berlin network (six station network). It is documented that in spite of the advanced phase observation modelling an internal relative baseline accuracy (utmost length 30 km) of the order of 3 to 5 ppm is achievable. In addition, the influence of orbital prior information on ground station measures, point position as well as accuracy, is demonstrated.