Civil-Net 系統之GNSS即時動態定位精度分析

近年來運用GNSS衛星基準網之網形法即時動態定位技術 (Network Real Time Kinematic, NRTK)已廣為測量人員使用，該技術具有減少儀具數量及人力、擴大作業範圍、誤差不隨距離增加、差分資料傳輸穩定以及可提高定位精度及可靠度等優點。在台灣地區，除內政部所建置的e-GNSS服務系統外，民間公司所架設之Civil-Net基準網，亦可作為相關定位需求之使用。本研究運用Civil-Net所提供之定位服務，以北、中、南、東之分區測點，以及高低海拔分布之測點，分別使用該系統提供之VRS 及FKP作業模式，於不同作業時段(早上、中午、傍晚)，進行其定位精度表現之評估。由定位坐標成果中誤差所代表之內部精度顯示，不論使用何種模式及作業時段，皆可滿足平面2 cm及高程5 cm之內政部作業規範之要求；而VRS在各區之表現差異（平面0.4 cm、高程0.9 cm）會較FKP（平面0.9 cm，高程2.5 cm）為小。但由基線長度較差所代表之外部精度顯示，VRS之分區差異（1.0 cm）卻會較而FKP（0.8 cm）為大。另在高低海拔之測試顯示，VRS的精度表現可優於FKP，且FKP模式在低海拔測點之成果較不穩定。

關鍵字

網形法即時動態定位；虛擬參考站；區域改正參數；內外部精度

並列摘要

In recent years, the NRTK technique using GNSS reference network has been widely used by the surveyors. It has many advantages in operation, such as reducing the instruments and man power, expanding the operating range, the error independing on the distance, providing stable data transmission, improving positioning accuracy and reliability. In Taiwan, in addition to the MOI-provided e-GNSS service system, the private company also set up a Civil-Net network to serve as needed. In this study, the Civil-Net system was mainly adopted to test its performance at some stations located in northern, central, southern and eastern Taiwan, as well as the stations with a lower and higher elevation. The operation modes of VRS and FKP, and the observations made at morning, noon, and evening, were conducted to assess the positioning precision and accuracy. The internal precision represents that 2 cm in plan and 5 cm in height, requested by the MOI, can be achieved for all different data sets; and the zone difference of using VRS (0.4 cm in plan and 0.9 cm in height) are smaller than that of using FKP (0.9 cm in plan and 2.5 cm in height). But the external accuracy represents that the zone difference using VRS (1.0 cm) is larger than that of using FKP (0.8 cm). Another test of the different elevations shows that VRS performed well than FKP, which provided less stable results at the lower elevation stations.