Vehicle localization on gravity maps

Efforts are underway to develop the capability for small unmanned underwater vehicles to use the Earth's gravitational field for autonomous navigation. A main aspect of navigation is vehicle localization on an existing gravity map. We have developed machine vision-like algorithms that match the onboard gravimeter measurements to the map values. In gravity maps there are typically a dearth of distinctive topographic features such as peaks, ridges, ravines, etc. Moreover, because the gravity field can only be measured in-place, probing for such features is infeasible as it would require extensive surveys. These factors, make the commonly used feature matching approach impractical. The localization algorithms we have developed are based on matching with contours of constant field value. These algorithms are tested on simulated data with encouraging results. Although these algorithms are developed for underwater navigation using gravity maps, they are equally applicable to other domains, for example vehicle localization on an existing terrain map.