Biao Lu^1,2,3, Franz Barthelmes², Min Li^2,3, Christoph Förste², Elmas Sinem Ince², Svetozar Petrovic², Frank Flechtner^2,3, Joachim Schwabe⁴, Zhicai Luo^5,6, Bo Zhong^1,7, Kaifei He⁸

1 School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, People’s Republic of China

2 GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany

3 Department of Geodesy and Geoinformation Science, Technical University of Berlin, 10623 Berlin, Germany

4 Federal Agency for Cartography and Geodesy, 04105 Leipzig, Germany

5 MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, People’s Republic of China

6 Institute of Geophysics, Huazhong University of Science and Technology, Wuhan 430074, People’s Republic of China

7 Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, Wuhan University, Wuhan 430079, People’s Republic of China

8 School of Geosciences, China University of Petroleum, Qingdao 266580, People’s Republic of China

Abstract: Shipborne gravimetry is an essential method to measure the Earth’s gravity field in the coastal and offshore areas. It has the special advantages of high-accuracy and high-resolution measurements in coastal areas compared to other techniques (e.g., satellite gravimetry, airborne gravimetry, and altimetry) used to obtain information about the gravity field. In this paper, we present the data processing strategies of shipborne gravimetry in GFZ. One key point is that the most suitable filter parameters to eliminate disturbing accelerations are determined by studying the GNSS-derived kinematic vertical accelerations and the measurement differences at crossover points. Apart from that, two crucial issues impacting on shipborne gravimetry are the seiches in some harbors and the squat effect in the shallow water. We identified that inclusion of GNSS-derived kinematic vertical accelerations can help to improve the shipborne gravimetry results at these special cases in the Baltic Sea. In the absence of the GNSS-derived vertical accelerations, the cutoff wavelength of the low-pass filter should be large enough to filter out these disturbing acceleration signals which causes a coarser spatial resolution of the gravity measurements. Therefore, the GNSS-derived kinematic vertical accelerations are very useful for optimum shipborne gravimetry. Finally, our shipborne gravimetry measurements are successfully used to verify the previous gravimetry data and improve the current geoid models in the Baltic Sea.

Keywords: Shipborne gravimetry, Chekan-AM, GNSS, FAMOS project, Baltic Sea