Abstract:

Global Navigation Satellite System (GNSS) networks are widely used for determining satellite orbit/clocks, monitoring crustal deformation and velocity field of the Earth as well as estimating the Earth’s rotation parameters. The data processing strategies comprise Double-Difference (DD) based baseline solution as well as un-differenced based Precise Point Positioning (PPP) solution. On the basis of fundamental GNSS observation equations, full-rank function models adopted by both strategies are respectively derived after identification of two distinct sets of datum parameters. Moreover, the potential pitfalls associated with both strategies are summarized. For instance, the estimable phase biases are biased by the clocks in context of DD strategy and thus become time-varying between adjacent epochs; with respect to PPP strategy, the integer nature of estimable ambiguities is deteriorated due to their absorption of phase biases. A modified strategy is proposed in this paper by means of determining a set of refined datum parameters so as to take advantage of benefits belonging to either DD or PPP strategies. Its main advantages involve: the solvability and the time-constancy of phase biases would largely reduce the number of unknowns and consequently improve formal precision of network solution. Furthermore, owing to well-kept integer nature of the estimable ambiguities, the reliability of network solution would be potentially strengthened after successful ambiguity resolution. Keywords: GNSS; reference network data processing; rank-deficiency elimination; time-varying parameters; time-constant parameters; precise point positioning

Key words: GNSS, reference network data processing, rank-deficiency elimination, time-varying parameters, time-constant parameters, precise point positioning