Sea surface heights around Taiwan from shipborne GPS measurements

• Main Authors: Chen, Yi-Ju, 陳逸如
• Other Authors: Hwang, Chein-Way
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/96942897612705942507

碩士 === 國立交通大學 === 土木工程學系 === 98 === 　　Sea surface heights (SSHs) from shipborne GPS measurements can potentially fill data gaps in coastal areas with bad altimeter observations caused by bad altimeter radar waveforms and poor geophysical corrections, and also be used for vertical datum connection. In this study, such ship-based SSHs are made possible using the 1-Hz GPS data collected in the campaigns of shipborne gravity from May to August, 2007. Precise point positioning (PPP), which uses zero differenced phase observables, is experimented for GPS positioning to determine SSHs, and its performance is compared with that of kinematic relative positioning (KRP). The accuracy of such GPS-derived SSHs is assessed by (1) static tests, (2) crossover difference analysis, (3) comparison with DNSC08 model. The computer packages Bernese and GRAFNAV are used for PPP, while Bernese, GRAFNAV , and TRACK are used for KRP. 　　The static tests at a long baseline case (>100km) shows that the RMS height variations from PPP and KRP are close, and are about 6-8cm. The RMS crossover differences of SSHs are 2-16 cm and 4-16 cm for Bernese PPP and GRAFNAV PPP, respectively. Such RMS values are 11-37cm and 5-24 cm for Bernese KRP and GRAFNAV KRP, respectively. A special case of TRACK KRP with 30-s GPS data yields a RMS value of differenced SSHs at 6-11 cm. About half of the research data sets agree with the positioning accuracy of KRP is better than PPP methods. However, PPP outperforms KRP especially in areas suffered from bad data quality of base stations, displaying the advantage of baseline independency. Comparisons between GPS-derived SSHs with DNSC08 SSHs lead to the following standard deviations (std.): 10-60 cm for both GRAFNAV PPP and KRP, which are the most consistent result of all softwares. With regard to Bernese, both Bernese PPP and KRP achieve good internal accuracy in crossover analysis by parameters estimation, but the external accuracy derived from the comparison with DNSC08 is worse than other softwares. 38-62cm for Bernese PPP and 13-58 cm for Bernese KRP demonstrate the feasibility of improving the process procedure. As a control group accomplished by using national base stations in 30 seconds data interval, the std. of TRACK KRP is 18-32 cm.