Objectives How to search intersections fast is the premise requirements of the quality evaluation of air-sea gravimetry data. With the continuous expansion of the scale of the air-sea gravity survey network and the emergence of irregular survey lines, the existing intersections search methods are hard to ensure that all the intersections can be quickly and accurately searched.Therefore, how to improve the searching efficiency and accuracy, has attracted much attention.
Methods We introduce the quad tree decomposition method to search the intersections of survey network, conduct the automatic refined subdivision near the intersections and then use the traversal comparison size to extract the overlapping area of the envelope rectangle of the main and auxiliary survey lines. By using rapid rejection judgment and repeated iterative search, the magnitude of indexes' number retained is equivalent to the actual intersections, which effectively avoids the large amount of redundant calculation. The method was programed and verified.
Results One experiment shows that the method can complete the search in only 0.28 s for the block EN01 airborne gravity data from gravity for the redefinition of the American vertical datum (GRAV-D) project, which has about 100 000 survey points; and another one shows that the search efficiency of the method for a survey network of 4 877 988 survey points is also significantly better than the existing methods and mature commercial software.
Conclusions This method uses traversal search to ensure 100% accuracy, and has high searching efficiency. It is universally applicable to the intersections' search of air-sea gravity network, and has excellent practical application effect.
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