使用GPS定位受到與距離相關的各種誤差影響，尤其是大氣效應，降低了逐時刻相位模稜(Ambiguity)求定的成功率，也降低了中長距離基線的定位精度。使用多參考站模式化(或內插)參考站與使用者間的各種誤差可以增加使用者移動距離、提升定位精度。
本研究目的在利用已知坐標找出參考站間相對對流層天頂向延遲（Relative Tropospheric Zenith Delay, RTZD），提供使用者內插改正參數，得到更精確的定位結果。主要工作分成三大部分：(1) 求解網形內各參考站間的RTZD；(2) 模式化這些RTZD；(3) 動態定位。
實驗結果顯示，若能正確的求解出參考站間的RTZD，並使用適當的內插函數，可使定位精度提升。

The distance-dependent GPS errors, notably atmospheric refraction, reduce the success rate of epoch-by-epoch ambiguity resolution, and limit the GPS positioning accuracy, especially for medium- to long-range baselines. Using multiple reference stations to model (or interpolate) the distance-dependent biases between the reference station and a rover can extend the distance or improve the positioning accuracy.
The objective of this research is to find out the relative tropospheric zenith delays (RTZD) between different reference stations by using known coordinates and to provide rovers with interpolated corrections for more precise positioning. The project consists of three major steps: (1) finding out the RTZDs between reference stations, (2) modeling the RTZDs, and (3) kinematic positioning.
Test result indicates that if the RTZDs between different reference stations can be resolved successfully, and a proper interpolation model is used, it is possible to improve the positioning accuracy.

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