An improved gravimetric geoid for Japan, JGEOID98, and relationships to marine gravity data

Abstract.

 A geoid model for Japan, JGEOID98, is determined on a 3 × 3 arc-minute grid in the non-tidal system by a one-dimensional Fast Fourier Transform method with EGM96 as a foundation. The model is referred to the GRS80 ellipsoid/ITRF89 frame. About 570 000 ship gravity data are adjusted for about 50 000 cross-over errors (COEs) and yield significant improvement: root mean square of internal and external COEs after adjustment are 6.8 and 10.4 mGal (0 and 24% of reduction), respectively. Compared with GPS at benchmarks, JGEOID98 shows improvement over JGEOID93 by 29% in short wavelength, and tilt reduction from 2.1 to 1.4 ppm. The remaining trend can be partly explained by gravity errors: overestimation of gravity induced from EGM96 east off Hokkaido, and underestimation south off Taiwan.