Abstract
For underwater gravity matching navigation, matching area selection has a significant impact on navigation accuracy. Since the changes of gravity anomaly between grids of gravity background map is different, when the underwater vehicle passes through the same matching area in different directions, the matching efficiency is also different. Therefore, for measuring the navigability of each grid point, a gravity anomaly sum vector-difference parameter is proposed. Its direction is with the largest comprehensive difference of local gravity anomaly, which can estimate the local matching direction. Its modulus value is the absolute difference of the gravity anomaly value between the central point and its local region. Compared to traditional scalar parameter, the vector parameter can obtain the matching suitability of the direction. In order to select efficient matching areas, the entropy method is applied to fuse the proposed sum vector-difference parameter with traditional gravity characteristic parameters to obtain the comprehensive characteristic parameter. Simulation results show that compared with the traditional method, the proposed method fully used the gravity information, and selected matching areas are more concentrated and continuous.
Highlights
Inertial navigation system (INS) is a widely used autonomous passive navigation system for underwater vehicles [1]–[4]
Comparing Figures, it can be found that the areas with large modulus values of sum vectordifference in Fig.2 (c) and (d) are areas with dense gravity anomaly contours, and the value of the area with good navigability can reach 26 or more
In the case where there is a symmetric cancellation of the matching direction of the region, we can perform the second statistical processing by defining the calculation range in combination with the sum vector-difference modulus to obtain multiple matching directions
Summary
Inertial navigation system (INS) is a widely used autonomous passive navigation system for underwater vehicles [1]–[4]. B. Wang et al.: Sum Vector-Difference-Based Matching Area Selection Method for Underwater Gravity-Aided Navigation interference information such as gravity measurement errors, it is difficult to perform completely accurate gravity matching and positioning, resulting in mismatch. Different from the traditional methods, we directly process the difference vector modulus of all directions of the sample grid by considering the mismatching rate, and integral these modulus to obtain the value of the difference degree of the local gravity anomaly at the grid. Due to the nature of the gravity field distribution, the directionality of the difference vector will be incompletely offset, resulting in the modulus of sum direction vector of points where the gravity information fluctuates greatly are small. We should consider both gravity anomaly value and spatial distribution, which are described as follows
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