管線圖資更新測量替代方法之探討——單雙距法

Alternative Operations for Pipeline Update Surveying–Single/Dual Ranging Mode

在一個以都會環境為主的區域中，採用標準的GNSS即時動態定位（Real Time Kinematic, RTK）來進行管線圖資更新測量作業，極有可能會受到GNSS衛星訊號遮蔽之影響，導致10%以上的施測點位無法取得品質可靠之RTK固定解坐標。取而代之的傳統作法，是在測點外圍之空曠區位利用RTK測設2個參考點，再配合全測站經緯儀（Total Station）之角距觀測，依光線法原理完成待測點之定位測量。然因管線作業單位在操作全站儀的技能恐有不足，故在簡化儀器操作的設計下，仍先以RTK測定2個固定解控制點，再僅運用距離量測來進行「單距法」及「雙距法」定位，以求建構可符合20 cm管線測量標準之替代性作業方法。由先期模擬與現地測試所得之成果可知，使用簡便的「單距法」定位模式的成功率較高，且可在模擬及現地測試場域獲得11-19 cm以內的平面坐標誤差。若能在現地作業時進一步顧及控制點間距（不宜過短）及待測點距離（不宜過長），另注意距離量測的精度與觀測線型（三點一線）的操作，「單距法」會是一套較具應用潛力的替代性作業模式。

In an urban environment, using GNSS Real Time Kinematic (RTK) for pipeline map updating operations is very likely to be affected by GNSS satellite signal obscuration. It is estimated that more than 10% of site is hardly obtain reliable quality of RTK fixed solutions. Instead, a traditional operation, using RTK to first set up two control points in the open area and then using total station to observe angle and distance, can complete positioning based on the principle of radiation survey. However, considering the skills of operating total station, a simplified operation of only using RTK to measure two control points with fixed solution and then taking distance measurement additionally is proposed to perform the ''single ranging'' and ''dual ranging'' positioning modes, in order to construct an alternative operation method that can meet the 20 cm pipeline surveying standard. Based on the results of preliminary simulations and field tests, it can be seen that the simple-to-use ''single ranging'' positioning mode has a higher success rate, and can achieve plane coordinate errors within 11-19 cm in all test sites. If the distance between two control points (should not be too short) and the distance to be measured (should not be too long) can be further considered, and also the accuracy of distance measurement and the setup of the observation line (three points in one line) can be noticed during on-site operations, ''single ranging'' mode will be a satisfied alternative positioning with higher application potential.