碩士 / 國立交通大學 / 土木工程系所 / 102 / Altimeter-derived sea surface heights (SSHs) in coastal areas can be seriously degraded because of the corrupted altimeter radar waveforms and poor geophysical corrections. The study is aimed at improving coastal gravity around Lanyu and Lutao by combine GPS-derived SSHs and retracked altimeter-derived SSHs here. GPS-derived SSHs at 1 Hz sampling frequency are from the shipborne gravity campaigns from 2007 to 2010, and satellites altimeter measurements are from the missions Cryosat-2,Geosat and ERS-1.
The sub-waveform threshold retracker is used to determine improved range tracking gates in the waveform data of Geosat and ERS-1. The Bernese 5.0 GPS computer package determines the positions of ships and therefore the SSHs, which are then filtered and resampled for gravity determination. The Inverse Vening Meinesz (IVM) formula is used to derive gravity anomalies from the retracked altimeter SSHs and from the GPS-derived SSHs. The resulting gravity anomalies are compared with shipborne gravity measurements, and the role of GPS-derived SSHs is assessed. Compared to the altimeter-only gravity field, the accuracy of the combined altimeter and GPS gravity field is improved by 0.13mgal around Lutao, and 0.43 mgal around Lanyu, corresponding to improvement percentages of 2.08% and 4.42% in the two regions. This shows the value of including GPS SSHs. Compared to the use of DTU 10 SSHS, the GPS-derived SSHS improve the gravity accuracy around Lanyu by 4.50% within 10-20 km to the coast, and by 8.76% within 10 km to the coast. This shows the value of including GPS-derived SSHs.
| Identifer | oai:union.ndltd.org:TW/102NCTU5015109 |
| Date | January 2014 |
| Creators | Chin, Mei-Fang, 覃美芳 |
| Contributors | Hwang, Chein-way, 黃金維 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 70 |
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