Absolute Gravity Network in Spain

摘要

Since the first absolute measurements of gravity in Spain (in 1882 by Joaquin Barraquer y Rovira) no absolute measurements were performed till 1989, by J. Makinen with a Jilag-5 absolute gravimeter. BKG of Germany and IMGC of Italy have measured six and three sites in Spain in the last decade of twentieth century. The National Geographic Institute of Spain (IGN) purchased the well known FG5 (number 211) and A-10 (006) absolute gravi-meters. In order to have a reference of measurements to other absolute gravimeters three International Comparison of Absolute Gravimeters have been performed: ICAG2001 at the Bureau International des Poids et Mesures (BIPM) in Sevres, ICSPAB03 at San Pablo de los Montes (Toledo, Spain) between European Center for Geodynamics and Seismology (ECGS) from Luxembourg and National Geographic Institute (IGN) from Spain, and finally Walferdange 2003 International Intercomparison in Luxembourg. Not only absolute but also vertical gradient and relative measurements were also executed at every station for processing and datum reduction on the floor, because absolute gravimeters have the nominal observation point around 1.30 and 0.70 meters above ground level. First results of Zero and a First order absolute gravity network will be presented, which hopefully will better the actual accuracies provided by the IGSN71 and RGFE73 and serve for geodynamic purposes.