Analysis and Selection of Global Marine Gravity/Gravity Gradient Aided Navigation Matching Areas

Abstract

With the development of underwater passive navigation in recent years, gravity or gravity gradient matching navigation are utilized to correct the accumulated navigation errors of inertial navigation system. The accuracy and success rate of gravity/gravity gradient matching navigation are seriously affected by the features of gravity changes in the sailing area. In this paper, a parameter named average gravity difference (AGD) was introduced here to express the level of gravity changes in a certain area. With the overall survey of global marine gravity, the AGD values of local areas were calculated and analyzed. After a series of experiments, the relationship of AGD values and navigation accuracy in local areas can be generally determined. As the criterion of selection of matching areas was induced, marine gravity matching areas for navigation can be selected. Simulation results showed that, take gravity as an example, the AGD values can range from about 0.6–2.7 mGal/nautical mile (1 nautical mile = 1 n mile = 1852 m) in different areas of the oceans around the world. With present technologies, gravity matching navigation could achieve an accuracy of 0.5 n miles in matching areas which have AGD values larger than 2.0 mGal/n mile. By this criterion, South China Sea, North Indian Ocean and some other areas can be selected. In these areas, better navigation results can be obtained since they have rougher gravity changes. These results would be significant for the development of gravity aided navigation technologies and the construction of underwater PNT system.