期刊名称：Bulletin of the Geographical Survey Institute
印刷版ISSN：0373-7160
出版年度：2010
卷号：58
出版社：Geographical Survey Institute / Ministry of Land, Infrastructure and Transport
摘要：This paper summarizes the effect of various noises on GEONET height time series and demonstrates how the state-of-art analysis technique can improve its quality with the results evaluated by simulations and actual observations. Three factors that may affect the GPS-derived height time series are investigated: 1) mismodeling of atmospheric delays; 2) load deformation by the atmosphere; and 3) load deformation by the ocean. It is found that: 1) the use of conventional mapping functions that are used in the current GEONET routine analysis may introduce spurious annual height variations up to 3mm, and these spurious signals can be considerably mitigated with the use of mapping functions based on numerical weather models; 2) annual height variations caused by the atmospheric loading are up to 3mm; and 3) the annual variations caused by oceanic loading deformations get larger toward the south, reaching 3mm in the Nansei Islands. It is confirmed that when these corrections are applied in the GPS analysis of GEONET data, the annual height variations of GEONET stations are largely reduced. Hence, it may now be possible to detect even these small movements related to the earthquake/volcanic activities that were formally obscured by the annual height noises, offering a hope that more accurate disaster prevention information could be provided.
