使用重力法大地起伏模型暨e-GPS觀測量獲得正高之方法與精度分析

Obtaining Orthometric Heights by Using a Gravimetric Geoid Model and e-GPS Observations: Methods and Accuracy Analysis

傳統上正高資訊是以水準測量方式獲得。隨著GPS技術的發展成熟，使用GPS聯合區域性大地起伏模型獲得正高之方式稱為GPS正高測量。近年來，網路即時動態RTK技術已成為國際趨勢，且內政部國土測繪中心已經成功建置一套網路RTK系統，簡稱為e-GPS或e-GNSS。若可成功使用e-GPS觀測技術進行GPS正高測量應可進一步提升其效率，因此本研究的主軸為探討e-GPS觀測量用於GPS正高測量之方法與精度分析。本文使用之方法為差分法以及修正面法，並在恆春半島進行測試。由實驗結果可知，修正面法之精度優於差分法，且其正高成果的絕對精度可以達到6公分。 Orthometric heights are traditionally obtained from spirit leveling. Along with the growing development of Global Positioning System (GPS), one can obtain orthometric heights from GPS measurement with a local geoidal model, and this procedure is called GPS leveling. In recent years, Network-based RTK GPS has become an efficient way of obtaining locational information. National Land Surveying and Mapping Center (NLSC) of Taiwan has successfully built up a Network-based RTK system called the e-GPS(or e-GNSS) system. Orthometric heights derived from e-GPS measurements can be used to further improve the efficiency of GPS leveling. Therefore, this paper aims at analyzing applicable methods and associated accuracies of orthometric heights derived from e-GPS measurements. Two methods, the differential method and the correction surface method, are adopted in the study. The test area is located in the Hengchun Peninsula. Experimental results show that the correction surface method is better than the differential method in terms of achievable accuracy, and the achieved accuracy is sufficient for various mapping requirements.

Orthometric heights are traditionally obtained from spirit leveling. Along with the growing development of Global Positioning System (GPS), one can obtain orthometric heights from GPS measurement with a local geoidal model, and this procedure is called GPS leveling. In recent years, Network-based RTK GPS has become an efficient way of obtaining locational information. National Land Surveying and Mapping Center (NLSC) of Taiwan has successfully built up a Network-based RTK system called the e-GPS(or e-GNSS) system. Orthometric heights derived from e-GPS measurements can be used to further improve the efficiency of GPS leveling. Therefore, this paper aims at analyzing applicable methods and associated accuracies of orthometric heights derived from e-GPS measurements. Two methods, the differential method and the correction surface method, are adopted in the study. The test area is located in the Hengchun Peninsula. Experimental results show that the correction surface method is better than the differential method in terms of achievable accuracy, and the achieved accuracy is sufficient for various mapping requirements.