- 學位論文
利用台灣GPS水準測量檢核 GOCE重力場模型精度
The Verification of GOCE Geoid Models Using GPS/Leveling in Taiwan
摘要
歐洲太空總署(European Space Agency, ESA)的GOCE (Gravity field and steady-state Ocean Circulation Explorer)衛星是目前唯一個利用衛星重力梯度測量技術(Satellite Gravity Gradiometry, SGG)的重力衛星。高空間分辨率的大地水準面模型製作，除了以陸測重力、船測重力和空載重力等方式來取得短波長資料以外，還包括利用現有的全球重力場模型，或其他衛星重力觀測資料補足長波長部分。由於GOCE衛星任務號稱可提供全球各地精度為1 cm之大地水準面，空間分辨率為100 km，因此本研究嘗試以台灣內政部水準點(約2000個點位)測量成果，採用幾何法求定大地起伏值(橢球高來自GPS測量；正高來自於水準測量)與GOCE、GRACE (Gravity Recovery and Climate Experiment)、EGM2008 (Earth Gravitational Model 2008)以及國立交通大學黃金維教授所提供的大地起伏模型做比較，驗證精度並探討GOCE的大地起伏模型在台灣與幾何法大地起伏的差值及其分布，目標是找到一個台灣用GPS/Leveling時可配合使用之最佳大地起伏模型。從分區比較結果得知，黃金維教授的大地起伏模型為最適合運用在台灣本島，並且此模型有修正參考基準(datum)，來降低誤差。而GOCE衛星因為只包含衛星本身資料，所以空間分辨率不足，目前還不適合單獨使用。未來我們可以期待EGM2008模型加入GOCE衛星資料之版本，但在應用前應先修正參考基準，以剔除資料之間的常差。本研究發現黃金維教授的大地起伏模型在台灣做GPS水準測量精度為5~10 cm；EGM2008精度為10~30 cm；GOCE精度為30~100 cm。
並列摘要
The GOCE (Gravity field and steady-state Ocean Circulation Explorer) Mission of the European Space Agency (ESA) is currently the only one using the satellite gravity gradiometry (SGG) technique for exploring the Earth¡¦s gravity. The satellite-observed gravity data is combined to the surface gravity measurements (on land, airborne or shipborne) in order to form a precise model with high-spatial resolution. One of the goals of the GOCE Mission is to provide 1-cm accuracy geoid with the spatial resolution of about 100 km. Hence, we attempted to verify the geoid model derived from GOCE and other gravity missions, such as GRACE (Gravity Recovery and Climate Experiment), CHAMP (CHAllenging Minisatellite Payload), EGM2008 (Earth Gravitational Model 2008), and a local geoid model with the geoid undulation observed at about 2,000 benchmarks in Taiwan by GPS leveling. The objective of this study is to analyze the models and find the best one that one could work with in GPS leveling work in Taiwan. We have categorized the entire Taiwan island into 5 different regions based on their geological settings in order to test the models. The result indicates the local geoid model released by the Ministry of the Interior, the so-called Hwang’s model, is the best choice due to its consistent datum with GPS and the inclusion of very dense surface, shipborne and airborne gravity measurements. The discrepancy of Hwang’s model to the GPS leveling is around 5-10 cm, whereas that of EGM2008 is around 30 cm, that of GOCE is 30-100 cm.