台灣地區海潮負載影響GPS高程變化之探討

海潮負載對於GPS之定位精度會造成影響，特別是在高程方向，影響量隨著觀測地點不同而異，大致上越接近海邊，海潮負載所造成的誤差越大，約可達到數公分甚至十公分的影響量。本研究探討在臺灣地區海潮負載對於GPS定位精度之影響，並使用國外近年來推出之海潮模式Andersen 2006、EOT08a、GOT4.7、TPXO.7.2與NAO.99b進行比較分析，評估海潮與GPS定位高程與相位之影響、比較不同海潮負載改正模式，最後利用潮位站與超導重力資料分析。海潮負載改正模式中發現，M2半日潮影響GPS高程可達0.6~1.4公分，M2半日潮高程經過海潮負載改正後減少為0.4公分以下，故海潮負載改正對高精度之GPS測量確實有其改正之必要。在各種海潮負載改正模式分析中以NAO.99b改正成果最好，特別在雲林與台南改正效果比其他模式好。 GPS其資料處理的基線越來越長，海潮負載的影響也越來越無法被抵銷，需依賴改正模式加以修正；近年來精密單點定位的應用越來越多，為求得更高精度的定位成果，以全球型或區域型海潮負載模式加以修正仍是必要。

關鍵字

全球定位系統；海潮負載；定位精度；改正參數

並列摘要

The ocean tidal loading (OTL) is an important factor for the GPS positioning, especially in the height direction. The influences are not the same in different places and the variations of GPS height are between few centimeters to twelve centimeters. In this paper, the influence of OTL for the GPS positioning in Taiwan was studied. Several OTL models such as Andersen 2006, EOT08a, GOT4.7, TPXO.7.2 and NAO.99b were compared to analyze the relationship between OTL and GPS height variations. Moreover, tide gauge and superconductive gravity data were employed to confirm the phenomenon of GPS height. We found that the M2 tide can influence the GPS height about 0.6-1.4 cm. After OTL correction, the GPS height variation can reduce to 0.4 cm. In five OTL models we tested, NAO.99b model has the best performance, especially in the western Taiwan. Therefore, the OTL correction is necessary for the high precise GPS positioning. The longer of the GPS baseline we choose, the harder of the influence from OTL effect can be reduced, so we need to use OTL model to correct this variation. In these years, the application of precise point positioning (PPP) is popular. To employ the global or regional OTL model is needed for high precise GPS positioning.