期刊名称：Bulletin of the Geographical Survey Institute
印刷版ISSN：0373-7160
出版年度：2018
卷号：66
页码：49-58
出版社：Geographical Survey Institute / Ministry of Land, Infrastructure and Transport
摘要：The Geospatial Information Authority of Japan (GSI) has carried out nationwide gravity surveys for about 60 years and provided a national gravity standard network, which has been widely used for various purposes such as calculation of orthometric heights, calibration of weighing instruments and exploration of underground structures. However, the gravity standard network needs to be revised since gravity changes have accumulated due to crustal deformation and it has become possible to measure gravity values more precisely thanks to recent improvements in gravimeters. Therefore, the GSI released an updated gravity network, named the Japan Gravity Standardization Net 2016 (JGSN2016), on 15 March 2017 for the first time in 40 years. JGSN2016 consists of gravity values at 32 fundamental gravity points and 231 primary gravity points (as of Mar. 2017). Each gravity value was calculated as follows: 1) determining the absolute gravity value of each fundamental gravity point based on absolute gravity measurements, 2) measuring gravitational differences along each baseline by relative gravimeters and 3) calculating the most probable gravity value of each primary gravity point by carrying out the net adjustment calculation using the values determined in 1). In the course of the process, the influences of solid-earth tide, atmospheric pressure, polar motion and ocean tide were adopted after removing outliers by statistical screening. In addition, the most appropriate combination of parameters for the net adjustment was determined by the Bayesian Information Criterion (BIC). The absolute gravimeters were calibrated through the annual comparison campaign with other domestic organizations which have absolute gravimeters. Thanks to these various improvements, JGSN2016 achieved precision of 3 and 11 μGal for the fundamental and primary gravity points, respectively.
