Allegedly these are useful in the search for oil and gas. Don't ask me how.
Technical University of Denmark: Global Gravity Field Model.
The global gravity field model shows the gravity variations over the global ocean as mapped by satellite. On land the field have been augmented with the best available terrestial gravity field com complete global coverage. Gravity changes are mainly caused by the changes in the attraction of mass under the surface.What changes in the attraction of mass are occuring under the surface?