Galathea-3: A global marine gravity profile

Between Aug 14, 2006 and Apr 24, 2007, and enjoying a considerable interest from the Danish authorities, the Danish public and the Danish media, the scientific expedition Galathea-3 circumnavigated the globe. Its domestic purpose was to attract the Danish youth to science. DTU Space, Technical University of Denmark, participated in the expedition with two experiments.

From Perth, Western Australia to Copenhagen, Denmark the exact position and movements of the ship were monitored using a combination of GPS, INS and laser measurements. The purpose was to measure the instantaneous sea surface topography. This paper reports on the second experiment in which a continuous marine gravity profile along the ship’s route was measured.

The focus of the paper is on the practical aspects of such large scale world wide operation and on the challenges of the data processing. Furthermore, the processed free-air gravity values are compared to 3 global models: EGM96, EGM08 and DNSC08. Even though the along-track resolution of marine data is higher than the resolution in any global gravity model (which influences the direct comparison of the collected marine data to the model) the statistics for the residual free-air gravity anomalies show, that EGM08 and DNSC08 are better models than EGM96 for all Galathea-3 legs.

Some areas along the ships route are quite challenging for modellers.