台灣e-GPS衛星基準站位移變化之研究

Abstract

台灣地區位於歐亞大陸與菲律賓板塊的縫合線上，菲律賓板塊以每年約7公分速度朝西北方向移動，導致台灣本島產生頻繁的地震，進而突顯出應用GPS基準站監測於防災研究之重要性。「精密單點定位」不同於傳統相對定位成果，所得坐標為絕對位置解，不受參考站、地區性坐標系統等條件限制。有鑒於此，本研究將分析內政部國土測繪中心建立之台灣e-GPS衛星定位基準站在國際地球參考框架中之位移變化，進行時間序列分析，再以該成果為比較基準，探討網路自動化精密單點定位計算服務CSRS-PPP解算成果可達精度。 空間分佈成果顯示，CSRS-PPP與國土測繪中心成果存在系統性偏差，N、E、h方向的差異量為0.142±0.0004 m、-0.313±0.001 m、0.019±0.004 m。時間序列成果顯示， 苗栗竹南、桃園復興、台北貢寮站在N、E方向之較差均值為（0.129±0.002 m、-0.346±0.008 m）、（0.134±0.003 m、-0.354±0.007 m）及（0.134±0.003 m、-0.354±0.008 m）。整體而言，CSRS-PPP靜態解算模式精度優於動態解算模式；若移除系統性偏差，就離散度而言，CSRS-PPP靜態解算模式精度已達公分等級。 基線長變化成果中，西部麓山區域之相對運動並不顯著，最大相對變形量為9 mm/yr。跨中央山脈與西部麓山區域之基線縮短量較前人成果增加約20 mm/yr。在2006~2007期間，中央山脈區域之基線伸長量呈減緩的現象，在量級上分別減少約26 mm/yr、20 mm/yr。海岸山脈地區與跨中央、海岸山脈區域之基線長變化印證東部海岸山脈地區仍存在往南移動的西北向擠壓，導致長濱以北的基線縮短變化較為緩和。

The island of Taiwan is located at the junction between the Eurasian plate and the Philippine plate. The Philippine plate moves northwestward at a speed of 7 cm/year, which leads to frequent earthquakes, therefore, using GPS base station monitoring on disaster prevention is quite important. Compared with the current relative positioning, Precise Point Positioning (PPP) refers to absolute positioning and it can also operate without restrictions such as using the base stations and local coordinate system. In consequence, this study analyses the deformation of Taiwan e-GPS base stations, which was built by National Land Surveying and mapping Center (NLSC), in International Terrestrial Reference Frame. By using the result of e-GPS station coordinates as comparison value, further experiments assess the accuracy of automated CSRS-PPP online positioning service. It is shown that there are systematic biases as compared with the solution from NLSC. The bias and standard deviation of the coordinate differences in N, E, h, 0.142±0.0004 m, -0.313±0.002 m, 0.019±0.004 m respectively for static solution. Based on static solution, the differences derived from the time series for stations JUNA, FUSN, GOLI in N, E, are (0.129±0.002 m, -0.346±0.008 m), (0.134±0.003 m, -0.354±0.007 m), and (0.134±0.003 m, -0.354±0.008 m) respectively. The magnitude of standard deviation is all under one centimeter. In conclusion, the CSRS-PPP static solution provides better accuracy than kinematic solution, and achieves the cm level. The result of baseline appears that the motion of the Western Foothills is not significant, and the maximum magnitude of deformation is 9 mm/yr. The baselines traversing the Central Range and Western Foothills yield shortening amount is much more 20 mm/yr than those observed previously. Compared with 2005~2006, the extensional deformation decrease 26 mm/yr for CSRS-PPP solution and 20 mm/yr for NLSC respectively in Central Range during 2006~2007. The length changes of baselines in the Coastal Range region as well as in traversing the Central Range and the Coastal Range are shown that there may be southward migration of the NW-vergent thrusting of the Coastal Range, which cause the decrease amount of shortening to the north of Changping.