[S-GD01] Geodesy and Global Geodetic Observing System

[SGD01-P06] A precise gravimetric geoid model for Japan that incorporates the airborne gravity data over the four main islands

*Koji Matsuo¹ (1.Geospatial Information Authority of Japan)

Keywords:Geoid, Gravity, Height Reference Frame

The Geospatial Information Authority of Japan has been conducting a nationwide airborne gravity survey over Japan since 2019 to construct a precise gravimetric geoid model for Japan. As of January 2023, the surveys over the four main islands of Japan (Hokkaido, Honshu, Shikoku, and Kyushu) have been almost completed. In this study, we report on the precise gravimetric geoid model for Japan that incorporates the airborne gravity data collected to date. The gravity data used are the GOCONS-TIM-R6 satellite gravity model, the Scripps V32.1 marine gravity model, 326,116 land gravity data, 443,338 shipborne gravity data, and 159,866 airborne gravity data. The airborne gravity data were confirmed to have an accuracy of approximately 1 mGal by internal evaluation using crossover data and external evaluation using existing gravity data. The geoid computation method was the remove-compute-restore Stokes-Hermert method with the hybrid Meissl-Molodensky modified spheroidal kernel. First, we examined the impact of introducing the airborne gravity data on the geoid computation, and confirmed that it results in the geoid change of -75 cm to +21 cm. The geoid change was especially large in coastal areas, and the largest change was observed in the coastal areas around Mutsu Bay (northern Honshu) and the Shiretoko Peninsula (northeastern Hokkaido). Comparison of the gravimetric geoid model computed in this study with 786 GNSS/leveling geoid height data shows that they are consistent with approximately 3 cm in terms of standard deviation (1σ).