Compilation and Evaluation of a Consistent Marine Gravity Data Set Surrounding Europe

Abstract

Various institutions have collected shipborne gravimetric measurements during the last decades. Due to different standards used for the processing of the observations and the necessary corrections, significant inconsistencies exist between different cruises. This contribution aims at producing a consistent marine gravity data set surrounding Europe, which can then be used for high precision geoid modelling, dynamic sea surface topography estimation, and other applications.

Besides our own marine gravity data holdings, data were collected from the Bureau Gravimétrique International (BGI), the National Imagery and Mapping Agency (NIMA, formerly DMA), and the National Geophysical Data Center (NGDC). The area of investigation is spanning the latitudes from 10 °N to 90 °N and the longitudes from 60 °W to 60 °E. The quality of the data varies between the individual cruises, as they originate from many projects at different epochs. Hence, systematic errors are likely to exist. Such errors can be significantly reduced by a crossover adjustment of the individual ship tracks. Because the track information was not available for all cruises, it had to be regenerated by different procedures. Furthermore, duplicate sources were removed before the crossover adjustment. The crossover adjustment is based on a bias per track error model. The adjustment of about 1.5 million observations in nearly 17,000 tracks led to a consistent high quality marine gravity data set. The RMS of the about 80,000 crossover differences is 15.5 mgal for the original data set, 8.4 mgal for an edited data set, and 4.7 mgal for the final crossover adjusted data set.

The second part of this contribution describes the evaluation of the marine gravity data set by altimeter derived gravity anomalies from different sources. These comparisons also prove the effectiveness of the crossover adjustment.