隨著科技的進步，全球定位系統(Global Positioning System, GPS)已被應用於許多需要導航及精密定位的科學及工程領域，因此如何精進其定位精度是一個被廣為探討及研究的課題。在一般及最先進的GPS資料分析方法中，定位精度在水平方向優於高程，其中一個最主要的原因就在於大氣水氣含量的變化所造成。
本文主要是探討對流層延遲效應與GPS高程坐標之間的相關性；研究中以標準大氣、地表氣象觀測及水氣微波輻射計三種氣象資料輔以參數估計及異質觀測修正的方法，對對流層延遲參數與GPS高程坐標之間的關係進行通盤且深入的討論。
我們研究結果發現，以地表氣象觀測資料取代標準大氣資料，進而配合參數估計方式，對靜態觀測的GPS高程坐標量值而言改變不大，約在數個mm等級。以地表氣象觀測資料取代標準大氣資料，進而配合異質觀測修正方式，對GPS靜態觀測的基線長度而言，影響量值約在cm等級，且基線重現性精度會提高；而對靜態觀測的GPS高程坐標而言，影響量值亦在cm等級左右，但多日平均標準差則較不穩定。以水氣微波輻射儀資料進而配合異質觀測修正方式，其結果大致與地表氣象觀測資料配合異質觀測修正方式雷同；但就晴朗天氣下的水氣微波輻射儀資料配合異質觀測修正方式時，其成果與參數估計方式比較，顯示出較佳的結果。對流層延遲量參數量值反應於GPS高程坐標的結果相當顯著。如欲提高GPS高程坐標精度，首要考量應當是確認所使用的對流層延遲量的正確性，再者使用異值觀測修正方法，應對觀測儀器有嚴格的資料篩選機制。

With the advancement of technology, Global Positioning System (GPS) observations have been used in a variety of scientific and technological disciplines requiring high-precision positioning. Hence, how to improve the GPS positing accuracy is constantly considered as an important research topic. In the GPS data processing schemes for general purposes and of most advanced, the positioning accuracy is much higher in horizontal coordinates than in the vertical coordinate. One of the major causes is in that the uncertainty and variation resulting from in atmospheric water vapor is very much significant.
In this dissertation, we investigate the relationship between tropospheric delay due to water vapor and the GPS positioning accuracy in the vertical coordinate. The tropospheric delay is obtained by three ways, standard atmospheric value (SAV), surface meteorological measurement (SMM), and water vapor radiometer (WVR) that are incorporated into the parameter estimation and external correction methods, respectively. Results based on thorough and complete investigations are consequently presented.
Several major findings are obtained from our investigations and stated behind. The vertical coordinate from static GPS positioning by use of parameter estimation method remains almost the same when SAV is replaced by SMM with deviation only on the order of mm. In contrast, the baseline derived from static GPS positioning may differ by an order of cm by use of external correction method when SAV is replaced by SMM. In addition, repeatability of the baseline is improved. Similarly, the vertical coordinate may vary on the order of cm, the average daily standard deviations vary unexpectedly large over a period of several days. Results from the use of WVR are similar to those from the use of SMM for the external correction method. Under clear sky conditions, results from WVR appear better when they are incorporated into external correction method than parameter estimation method. This indicates the significant impact of the tropospheric delay on the vertical coordinate determination by GPS positioning. Apparently, it is important to acquire accurate tropospheric delay in order to assure high-accuracy of vertical coordinate determination. Meanwhile, it is crucial to utilize high-quality data when external correction method is implemented.

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