Implementing Marine Gravimetry Test Using Strapdown Gravimeter in the South China Sea

Yu, R.; Xu, X.; Zhao, L.; Wang, M.; Cai, S.; Cao, J.; Wu, M., and Lu, S., 2020. Implementing marine gravimetry test using strapdown gravimeter in the South China Sea. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 382–388. Coconut Creek (Florida), ISSN 0749-0208.As one of the major kinematic ways for surveying purpose in the sea region, shipborne marine gravimetry is important to get high accuracy and resolution gravity information. Until today, after decades of development and innovation, marine gravimetry is still a main and important mean of obtaining gravity data from the vast ocean areas. Based on the former generation gravimeter, SGA-WZ02 designed by NUDT has a further development. With this gravimeter, a marine test in the South China Sea was implemented for 40 days. The purpose was assessing feasibility and accuracy of this gravimeter for marine gravimetry. Surveying region was near the Xidutan area and the East Island in the South China Sea and total area of the measuring region is about 442.55 km2 with a total of 884.7 km surveying distance. In this test, 15 east-west parallel lines separated by 1 km and 2 north-south inspection lines were measured. The average line distance is 14 km and the speed is about 10 kn. Since there were no repeated measurement lines, this paper used cross over differences among 17 lines to evaluate the performance. In marine gravity measurement experiments, it is particularly important to use GNSS precision point positioning (PPP) technology to measure the accurate position and velocity information of the carrier. Totally, 30 cross over points were obtained in the test and the average value of these points is -0.42 mGal using 300 s FIR filters which means the resolution was about 750 m. The root mean square value is 0.64 mGal that the result was at the same level of accuracy as the current mainstream marine gravimeters. It indicates that the SGA-WZ02 strapdown gravimeter can be used for marine gravimetry applications in geodesy and geophysical survey activities.