以GPS技術量測安平港潮位之探討

For Monitoring oceanic Tide of An-ping Port by Using GPS Techniques

國家級高程基準的維護，有賴於潮位站提供精準、正確的潮位資料，目前臺灣海水面資料皆來自潮位站潮位儀測量之成果，但是否可利用GPS定位技術，亦能達到此目的，為本研究之目的。在潮位站附近海水面上設置GPS浮標，持續量測海水面之變化，並與潮位站共構之GPS連續追蹤站，進行動態相對定位，可解算出GPS浮標瞬間位置，再擷取其橢球高，以時間序列繪製高程分佈圖，此曲線就代表海水面隨時間變化之瞬間位置。本研究係以設計完成之多天線浮標，在安平港潮位站旁海面施放測試，結果與潮位儀比較，估算誤差為0.91cm，另外，亦利用同時接收GPS左旋與右旋訊號之整合天線，進行GPS直接與反射訊號相位觀測、訊號反射點座標定位分析與海面海浪之水位高程變化計算。在分析與計算過程中，可估算出波長與週期，在安平港潮位站進行6小時之RGPS水位變化實驗，將結果與潮位儀、水準尺之量測進行比較，偏差約1.0~3.0cm，由此可驗證RGPS與潮位儀之水位量測，具有同等級精度。

To maintain the national height datum is based on the monitoring of tidal gauge that provides an accurate and precise tidal record. Nowadays in Taiwan area the main data set of height datum is almost gathered from tidal gauge record. That it is possible to collect data using GPS techniques is the purpose of this research.To establish GPS buoy above the surface near Tide Gauge for continuously monitoring sea level change and dealing with the dynamic relative positioning of the GPS tracking station integrated with the Tide Gauge, the instantaneous position of GPS buoy can be solved. Then based on ellipsoid height of each point and time series, the curve of height distribution is drawn. The curve can represent the instantaneous position of the sea surface. On the other hand, the application of a highly integrated GPS receiver that employs reflected GPS signals to measure the sea level was performed at Ann Pin Harbor. Both RHCP and LHCP antennas are employed to simultaneously obtain direct and reflected signals. The objective of this study is to use the carrier phase of Li and L2 band reflected signals, and direct signals to determine the sea level at coastal area, as well as to distinguish wave length and wave cycle time. The difference among the result from RGPS, tide gauge, and staff meter at Ann Pin Harbor are approximately 1.0~3.0 cm with 6 hrs of RGPS observations. It is proved that the results from RGPS measurement have the same accuracy as the tide gauge.