The marine gravity field reference map is a tool that describes the spatial distribution of that field, and possesses unique advantages such as passivity, stability, anti-interference, and irregularity of the distribution when using a gravimeter to acquire gravity information at the location of an underwater submarine. Such methods are mainly based on sufficiently numerous variations of measured physical or geometrical parameters in spatial distribution, and, through comparison with pre-stored reference maps, correct matching is achieved. The geophysical field-aided navigation method primarily uses gravity and magnetic fields and sea floor terrain data measured by an underwater submarine to perform matching and comparison with graphical data stored in advance, thus obtaining accurate estimates of locations and correcting the INS errors. To compensate this deficiency of the INS, various integrated navigation systems centered on inertial navigation have been developed, and an inertial/gravity integrated navigation system based on characteristics of the geophysical field has become an effective approach for navigation by underwater submarines under conditions of long-range underwater navigation over a long period. The INS alone can hardly provide accurate navigation information over a long period of time. The inertial navigation system (INS) is one of the major approaches for underwater navigation, but errors of the INS accumulate over time and increase gradually. The gravity characteristic parameters identified herein and characteristic values calculated in various zones provide a reference for the selection of navigation area and planning of sailing routes under conditions requiring certain navigational accuracy. In particular, accuracy in regions around the South China Sea and Sulu Sea was the highest, better than 1.5 n miles.
Given the precision of current gravimeters and the resolution and accuracy of reference maps, the location accuracy of gravity matching in China’s Western Pacific area is ~1.0–4.0 nautical miles (n miles). Studies indicate that the new parameters may better characterize the marine gravity anomaly. The influence of gravity variations on the accuracy of gravity matching-aided navigation was analyzed, and location accuracy of gravity matching in different zones was determined. Those characteristic values were calculated for 13 zones (105°–145° E, 0°–40° N) in the Western Pacific area, and simulation experiments of gravity matching-aided navigation were run. In this study, based on marine gravity anomaly reference maps, new characteristic parameters of the gravity anomaly were constructed.
The variation of a marine gravity anomaly reference map is one of the important factors that affect the location accuracy of INS/Gravity integrated navigation systems in underwater navigation.