Towards a cm-geoid for Hungary: Recent efforts and results

Some steps were taken recently for Hungary aiming at the determination of g eoid heights with a cm-accuracy. The present HGTUB98 gravimetric solution w as based on terrestrial gravity data, height data and the EGM96 geopotentia l model; and was computed with the 1D Spherical FFT method, The gravity dat a were used in the area 45.5 degrees < phi less than or equal to 49 degrees , 16 degrees less than or equal to lambda less than or equal to 23 degrees, the resolution of the grid was 30 " x 50 ". The DTM used had a resolution of 1 km x 1 km. Our solution was evaluated using GPS/levelling data at 340 and 308 points r espectively and at 138 vertical deflection points. We have compared our sol ution to the European EGG97 geoid solution, the gravimetric solution HGR97B developed by A. Kenyeres and the litospheric geoid solution by G. Papp. We have correlated our recent HGTUB98 solution to the Moho model of Central E urope. The comparison with GPS/levelling yielded respectively an accuracy o f +/-8.7 cm and +/-4.4 cm (in terms of standard deviation) when a linear tr end was removed. The comparison of the 1D planar FFT solution for the defle ctions of the vertical with 138 astrogeodetic deflections yielded an accura cy tin terms of standard deviation) of +/-0.62 " and +/-0.52 " for xi and e ta, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.