In 2008, we generated a version of satellite gravity known as Trident by stacking three independently derived solutions of free air gravity from satellite altimeter data by three different authors, with the result that this became the most reliable, coherent and robust satellite gravity solution available.
The satellites used were the ERS-1 and Geosat satellites which flew in the 1980s and 1990s. The average track spacing of the satellite data at the equator is ~4-5 km. The three solutions used to create Trident were:
- Getech’s 2004 solution
- DNSC (Danish National Space Centre) DNSC08
- Sandwell and Smith, version 16.1
All three solutions were created by re-picking the timing of the satellite radar return pulse from the sea surface, editing, levelling and conversion from sea surface heights to free air gravity.
The Trident data are provided to clients as 2 km grids of free air gravity, Bouguer anomaly and isostatic residual gravity.
In mid-2013 Getech commenced a 3-year Multi-Satellite Altimeter Gravity Project incorporating additional altimeter data from the new Cryosat-2, Jason-21 and Hy-2A satellites increasing in the amount of track data on which the final gravity solution is based by more than 100%.