Abstract
We developed a refined gravimetric geoid model for Japan on a 1 × 1.5 arc-minute (2 km) grid from a GOCE-based satellite-only global geopotential model and a regional gravity field model updated in this study. First, we have constructed a regional gravity field model for Japan using updated gravity datasets together with a residual terrain model: 323,431 land gravity data, 77,389 shipborne marine gravity data, and Sandwell’s v28.1 altimetry-derived global marine gravity model. Then, the geoid was determined with the gravity field model. The methodology for gravimetric geoid determination was based on the remove–compute–restore technique with Helmert’s second method of condensation of topography (Stokes–Helmert scheme). Here, the hybrid Meissl–Molodensky modified spheroidal Stokes kernel was employed to minimize the truncation error under an appropriate combination of different kinds of gravity data. In addition, a high-resolution GSI-DEM on a 0.4 × 0.4 arc-second (10 m) grid, together with the SRTM-DEM on a 7.5 × 11.25 arc-second (250 m) grid, was utilized for precisely applying terrain correction to the regional gravity field model. Consequently, we created a gravimetric geoid model for Japan, consistent with 971 GNSS/leveling geoid heights distributed over the four main islands of Japan with a standard deviation of 5.7 cm, showing a considerable improvement by 2.3 cm over the previous model (JGEOID2008). However, there remain some areas with large discrepancies between the computed and GNSS/leveling geoid heights in northern Japan (Hokkaido), mountainous areas in central Japan, and some coastal regions. Since terrestrial gravity data are especially sparse in these areas, we speculated that the largeness of the geoid discrepancies there could be partly attributed to the insufficient coverage and accuracy of gravity data. The Geospatial Information Authority of Japan has started airborne gravity surveys to be covered over the Japanese Islands, and in future, we plan to develop a geoid model for Japan further accurately by incorporating airborne gravity data to come.
Highlights
The geoid is the equi-geopotential surface best fitted to the global mean sea level
In the Stokes–Helmert scheme, a gravimetric geoid model is composed of three components ( NGGM, Ncroes, and δNPIDE ) expressed in Eq (5)
The Japanese gravimetric geoid model has been greatly improved by incorporating a Gravity field and steady-state Ocean Circulation Explore (GOCE)-based global geopotential model (GGM), updating the regional gravity field model, and adopting the FEO
Summary
The geoid is the equi-geopotential surface best fitted to the global mean sea level. Though classical geoid determination is restricted to regional computations using the astro-geodetic techniques (Drews and Adam 2019), by grace of the enhancement of space geodesy techniques, the two approaches described below are mainly used toOne approach adopts direct measurements of geoidal undulations at points on the Earth’s surface using the combination of spirit leveling and gravity measurements, and GNSS positioning. This approach is more reliable than GNSS/leveling for a high-resolution geoid modeling in a regional or global scale, because gravity anomalies are comparatively easy to measure over a wide area without cumulative errors in distance. Fill‐in gravity data The computation of a gravimetric geoid model by the RCR technique implements the regional integration of terrestrial gravity over some limited spatial area.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
