4:30 PM - 4:45 PM
[SGD02-11] An attempt to improve coastal geoid determination by introducing airborne gravity data and a marine residual terrain model
Keywords:Geoid, Gravity
Precise geoid determination at the coastal zones is particularly challenging due to the difficulty in obtaining high-quality gravity data there. In the latest gravimetric geoid model for Japan, JGEOID2019 (Matsuo and Kuroishi, 2020), 77,389 shipborne gravity data and an altimetry-derived marine gravity model were used as the gravity data over the ocean surface. Most of the shipborne gravity data (about 75,000 points) were provided by the Hydrographic and Oceanographic Department of the Japan Coast Guard and were observed after 1983 when the data quality was considered to be relatively high. The spatial distribution of the shipborne gravity data has a wide range of data gaps in the areas around Hokkaido, Kyushu, the western Japan Sea, and the northern Kanto coastal area, etc. The data gaps were supplemented by an altimetry-derived marine gravity model; however, the marine gravity model may contain errors of over 20 mGal within 10 km of the coastal zones, which may reduce the computation accuracy of the gravimetric geoid model there. Consequently, there are large discrepancies between the gravimetric geoid model and the GNSS/leveling geoid data in some coastal areas of Japan.
In this study, we attempt to improve coastal geoid determination by introducing airborne gravity data and a marine residual terrain model. The airborne gravity data, which have been collected on nationwide surveys by the Geospatial Information Authority of Japan since 2019, mainly contains gravity information at the medium wavelength components. The marine residual terrain model, which is estimated based on a bathymetry digital elevation model, mainly contains gravity information at the short-wavelength components due to gravitational attractions of the oceanic topography. In addition, the shipborne gravity data from 1968 to 1982, which were excluded from JGEOID2019, were screened by airborne gravity data and a marine residual terrain model, and then introduced into the geoid computation. The accuracy of the geoid computation results will be evaluated by comparing them with the GNSS/leveling geoid data at the coastal zones.
In this study, we attempt to improve coastal geoid determination by introducing airborne gravity data and a marine residual terrain model. The airborne gravity data, which have been collected on nationwide surveys by the Geospatial Information Authority of Japan since 2019, mainly contains gravity information at the medium wavelength components. The marine residual terrain model, which is estimated based on a bathymetry digital elevation model, mainly contains gravity information at the short-wavelength components due to gravitational attractions of the oceanic topography. In addition, the shipborne gravity data from 1968 to 1982, which were excluded from JGEOID2019, were screened by airborne gravity data and a marine residual terrain model, and then introduced into the geoid computation. The accuracy of the geoid computation results will be evaluated by comparing them with the GNSS/leveling geoid data at the coastal zones.