Method of separating dipole magnetic anomaly from geomagnetic field and application in underwater vehicle localization

Because dipole magnetic anomaly caused by ferromagnetic object or geologic structural change is mixed with geomagnetic field and difficult to calculate its magnitude, it lead to a problem for automatic underwater vehicle (AUV) localization aided by geomagnetic anomaly. To solve this issue, a novel AUV localization method introducing draft depth is put forward, where vertical position of AUV relative to magnetic dipole target can be directly calculated from twice draft depth measurement. The algorithm related to the localization method is deduced theoretically and simulated numerically. These results all show that the novel localization method behaves high precision when vehicle is far away from the target. The measured errors such as draft depth and target magnetic field gradients act effect on localization accuracy. The relationship between localization precision and target distance are respectively analyzed and discussed. Based on these investigations, another possible localization method for AUV whose height relative to sea bed obtained by single measurement is brought forward and at the same time its application limitation is pointed out. We deduce and simulate an approach calculating target magnetic moment from AUV position parameters and the simulation indicates that target magnetic moment can be obtained precisely.