Accuracy Analysis of UAS Imagery Using RTK/PPK-assisted Aerial Triangulation

摘要

Recently, unmanned aerial systems (UASs) are commonly used in aerial mapping, since their operational flexibility and practicability combined with low cost implementations and maintenance. Due to payload limitations of UAS, it is difficult to equip a tactical grade POS (Positioning and Orientation System) devices. Meanwhile, on-site ground surveying of control points (GCPs) is a time consuming and cost ineffective process with a large amount of field activity. Moreover, some forest areas are not possible to obtain GCPs, which hampers the accurate mapping in these areas. For geo-referencing demands, the RTK (Real Time Kinematic) and PPK (Post Processed Kinematic) are introduced in this research. The RTK can offer instant position of the flying trajectory in centimetre accuracy level. Besides, it can assist the launch and landing of an UAS. Unlike RTK, PPK doesn't rely on the communication between base station and rovers. Although PPK can't process position in real-time, it can provide more accurate initial position of image due to the use of precise ephemeris. Therefore, in this study we use a fixed-wing UAS as platform that equipped with a Sony ILCE A6000 digital camera. The goal is to evaluate the positioning accuracy of RTK and PPK assisted aerial triangulation without GCPs. In which, several ground control/check points measured by e-GNSS are used to estimate the capability and accuracy of the results.