內政部東沙衛星追蹤站天線主點與副點相關位置檢測

Relative Positioning Check of the Antenna Center, MOI Dongsha Satelite

內政部東沙衛星追蹤站，為八個由內政部於八十二及八十三年度設置之全天候二十四小時連續不斷接收衛星資訊之資料收集站之一。此八個衛星追蹤站，可視之為TWD97 基準之框架。衛星追蹤站之設置依照嚴謹之規範，天線設置於鋼筋混凝土澆築之柱狀體上。由於東沙島之土壤由風化之珊瑚礁所構成，其膠著程度較低。該站之天線柱是否有傾斜，於近年引發關注。本研究採用GPS 與全測站經緯儀，以實測方式探討主天線與副點相關位置。經初步測量與分析結果，顯現三個副點目前相互間幾何位置與公告坐標之一致性在公厘級，而主天線與副點相關位置已有大於一公分之位移。 Dongsha Satellite Tracking Station is one of the eight TWD97 framework stations. This stationwas established in 1994 by Ministry of Interior, and continuously operating 24 hours each day. Theconstruction of this station followed rigorous guideline. The GNSS antenna is mounted on the top ofa re-enforced concrete pillar. Because the top soil of Dongsha island is mainly the decomposed coralreef, the cementation level is relatively low. Whether this antenna pillar has tilted due to itsfoundation problem causes concerns recently. In this study, both the GPS surveying andtriangulateration surveying with a total station are performed to investigate the relative positionbetween the antenna center and surrounding monuments. It is found that the antenna center hasmoved more than one centimeter as compared with the published coordinates, while the relativeposition difference of the three surrounding stations is in the millimeter level.

Dongsha Satellite Tracking Station is one of the eight TWD97 framework stations. This stationwas established in 1994 by Ministry of Interior, and continuously operating 24 hours each day. Theconstruction of this station followed rigorous guideline. The GNSS antenna is mounted on the top ofa re-enforced concrete pillar. Because the top soil of Dongsha island is mainly the decomposed coralreef, the cementation level is relatively low. Whether this antenna pillar has tilted due to itsfoundation problem causes concerns recently. In this study, both the GPS surveying andtriangulateration surveying with a total station are performed to investigate the relative positionbetween the antenna center and surrounding monuments. It is found that the antenna center hasmoved more than one centimeter as compared with the published coordinates, while the relativeposition difference of the three surrounding stations is in the millimeter level.