Figure 4 Topography on the study area of Bilogora mountainous For the accuracy assessment, fitting was made on a set of six GNSS/levelling points located in the study area, The red line shows the behaviour of the standard devi- ation for the input gravity data. Even if the RMS would be neglected, the last three models could be eliminated regarding the too large interval of extreme values showing incapability to compute a solid consistent quasi-geoid model from such a small density of terrestrial gravity data. Observing other models, it is visible how the gravity