衛星導航系統備援方案之地面信標定位模擬

Simulated Positioning of Using Terrestrial Beacons as a Backup for Satellite Navigation System

在衛星導航屬於艱困環境中的都會區內，建物及結構物可能會遮蔽許多GNSS衛星訊號，也可能會受到人為的電波干擾，導致衛星數量、幾何結構及定位精度等，出現明顯的惡化，甚至無法成功定位。針對此類困難之克服，本研究針對可行之地面信標，模擬產生相關之測距資料，並行空間交會定位運算，以探討地面信標觀測量運用於導航定位之成果特性。由模擬測試之定位誤差可知，在呈現高度相關之成果表現中，地面信標之布設間距愈短，或是信標之架設高度愈高，其平面與垂直方向之定位誤差皆可愈小。若以信標間距5 km及架設高度20 m之定位為例，最佳幾何性布設條件下之平面及垂直誤差可分別優於0.2 m及3 m；另信標使用數量由4具提高至8具時，其定位誤差可降低至少70%。當地面信標觀測量運用於50 m航高之無人機時，其定位誤差可較同等模式運作下之地面載具的表現更佳。

GNSS satellite signals may be blocked by surrounding buildings and structures, or interfered by specific frequencies of radio waves. Satellite positioning in metropolitan areas may significantly affect the satellite number, distribution geometry and positioning accuracy, or even lead to positioning failure. In response to overcome such difficulties, this study investigates the performance of using terrestrial beacon-based observation data, as applied to navigation positioning, by simulating the ranging data and carrying out the spatial resection. According to the positioning errors of simulation testing with highly correlated characteristics, it shows that the shorter the distance interval between terrestrial beacons or the higher the beacons are set, the smaller the positioning errors in both horizontal and vertical components. For example, if beacons are located at a distance interval of 5 km with an altitude of 20 m, and in the optimal geometric layout, the horizontal and vertical errors can be less than 0.2 m and 3 m, respectively. Moreover, when the beacons in use are increased from four to eight, the error can be reduced by 70%. When the terrestrial beacon-based observation data are applied to unmanned aerial vehicles flying at a height of 50 m, the positioning error is smaller than that of ground vehicles operated in the same mode.