The paper presents an attempt to assess how random errors and systematic errors in gravity data affect the quality of the geoid model when it is computed using the FFf technique. Three groups of numerical tests were conducted with the use of gravity anomalies for Poland on 2' x 2' and 5' x 5' grid and with simulating random and systematic errors. In the first test, the effect of random errors on calculated geoid undulations was investigated, in the second one - the effect of systematic errors, and in the last one - the combined effect of both random and systematic errors. The effect of density of data set on the propagated error in geoid height was also examined. The results of numerical tests made possible to evaluate the effect of random errors as well as systematic errors on the accuracy of computed geoid undulation. They were also useful in evaluating the quality of the gravimetric quasigeoid model for Poland.

In this study, several variants create and choose of a local quasi-geoid model in Poland have been considered. All propositions have a source in European Gravimetric Geoid models – EGG2008 and EGG2015, which are purely gravimetric models of reference surface. In the course of this work, each model has been analyzed in various ways: without any corrections, by parallel shifting of residuals, by the 7-parameter conformal transformation and by fitting residuals by 4- and 5-parameter trigonometric polynomials. Eventual corrections were based on points of national GNSS/levelling networks (EUVN, EUVN_DA, POLREF, EUREF and ASG-EUPOS eccentric points). As a final result of this study, a comparison of the accuracy of selected models has been carried out by RMSE statistics and maps showing spatial distribution of residuals and histograms. Validation has shown that the maximum achievable accuracy of the EGG models is approximately 2 cm for the ETRF2000 reference system and approximately 8 cm for ETRF89. In turn, fitting with the use of different mathematical methods results in an improvement of the standard deviation of residues to the level of 1.3–1.4 cm. The conclusions include an evaluation of considerations for and against the use of models based only on EGG realizations and, on the other hand, fitted to the points of Polish vertical network. Its usefulness is strictly connected with needs of the definition of up to date quasi-geoid model for the new realization of heights system in Poland, based on EVRF2007 frame.

A method of the improvement of the total station observations 3D adjustment by using precise geoid model is presented. The novel concept of using the plumb line direction obtained from the precise geoid model in combined GPS/total station data adjustment is applied. It is concluded that results of the adjustment can be improved if data on plumb line direction is used. Theoretical background shown in the paper was proved with an experiment based on the total station and GPS measurements referred to GRS80 geocentric reference system and with the use of GUGIK2001 geoid model for Poland.