Validation of ERS-1 and High-Resolution Satellite Gravity with in-situ Shipborne Gravity over the Indian Offshore Regions: Accuracies and Implications to Subsurface Modeling

Abstract

Geoid and gravity anomalies derived from satellite altimetry are gradually gaining importance in marine geoscientific investigations. Keeping this in mind, we have validated ERS-1 (168 day repeat) altimeter data and very high-resolution free-air gravity data sets generated from Seasat, Geosat GM, ERS-1 and TOPEX/POSEIDON altimeters data with in-situ shipborne gravity data of both the Bay of Bengal and the Arabian Sea regions for the purpose of determining the consistencies and deviations. The RMS errors between high resolution satellite and ship gravity data vary from 2.7 to 6.0 mGal, while with ERS-1 data base the errors are as high as 16.5 mGal. We also have generated high resolution satellite gravity maps of different regions over the Indian offshore, which eventually have become much more accurate in extracting finer geological structures like 85° E Ridge, Swatch of no ground, Bombay High in comparison with ERS-1satellite-derived gravity maps. Results from the signal processing related studies over two specific profiles in the eastern and western offshore also clearly show the advantage of high resolution satellite gravity compared to the ERS-1 derived gravity with reference to ship gravity data.

Keywords:

• Satellite gravity
• Indian offshore
• validation
• power spectral density
• coherences
• subsurface modeling

Acknowledgements

The authors are very much thankful to Prof. C. Hwang, National Chiao Tung University, Taiwan, for providing high resolution geoid/gravity data and the related software. They also thank the anonymous referees for their suggestions for improving this paper. They are also thankful to Dr. K. L. Majumder, Ex-Dy. Director, RESIPA/SAC, and Dr. Ajai, Group Director, MESG/RESIPA/SAC, for their keen interest in this study. Rudradeb Bhattacharyya wishes to thank the Council of Scientific and Industrial Research, New Delhi for his fellowship. Part of the work was carried out by NIO scientists—their institute's contribution number 4189.