Contraste de geoides gravimétricos con observaciones de nivelación geométrica y GPS en la comunidad de Galicia

Résumé

This work describes the physical and contrast of different geoid models availables, applied in the northwest of Spain, in the community and neighbouring of Galicia and northern Portugal. The model contrast is done by comparing the direct undulations with the one calculated on levelling nails using REDNAP (Spanish Network of Highprecision Levelling); in which it is observed and calculated the ellipsoidal height using GPS measurements in static mode with time no less than 3 hours, also vertices are observed in the REGENTE (Spanish Geodesic Network for Space Technics) network from the National Geographic Institute (IGN) and the Portugal National Geodesic Network (RGN). The fiducial points are active antennas from the ERGNSS, ITACYL, and GALNET network. Observations were done on 136 points, 116 nails REDNAP and 20 geodetic vertices, one of them was made in Portugal. The test models used in this work were IBERGEO95 (Geoide Ibérico 1995), EGM96 (Earth Gravitational Model 1996), EGG97 (European geoid model EGG97), IGG2005 (Iberian Gravimetric Geoid of 2005), EGM08 and an adapted version of EGM08 to REDNAP by IGN, and finally EGM08REDNAP. Nail separation was chosen to be about 10 km, and the position was the same that the one measured by IGN in ER. The results showed differences in REGENTE vertices with official coordinates probably because of the different frame system used, but also notes that are more accurate than indicated by IGN. Levelling nails are in 97% of the cases a better precision than 12 mm. Contrasting the models verified that the best fit is the most updated one, and it showed that the precision indicated by official organizations in relation to EGM08REDNAP is significantly lower than specified.