On the adjustment of combined GPS/levelling/geoid networks

Abstract. A detailed treatment of adjustment problems in combined global positioning system (GPS)/levelling/ geoid networks is given. The two main types of ‘unknowns ’ in this kind of multi-data 1D networks are usually the gravimetric geoid accuracy and a 2D spatial field that describes all the datum/systematic distortions among the available height data sets. An accurate knowledge of the latter becomes especially important when we consider employing GPS techniques for level-ling purposes with respect to a local vertical datum. Two modelling alternatives for the correction field are presented, namely a pure deterministic parametric model, and a hybrid deterministic and stochastic model. The concept of variance component estimation is also proposed as an important statistical tool for assessing the actual gravimetric geoid noise level and/or testing a priori determined geoid error models. Finally, conclu-sions are drawn and recommendations for further study are suggested. Key words. Geoid evaluation á GPS height transformation á Multi-data 1D networks á Adjustment