Application of Low Cost GPS/BDS Receiver in UAV Precise Navigation and Positioning

Recently, unmanned aerial vehicle (UAV) technology has been growing rapidly and widely used in civil applications, such as aerial mapping, precise agriculture, power line patrolling. However, most of high precision position and orientation systems (POS) are still heavy and expensive, so they are still unpractical to be equipped on UAV. In this study, we investigated the feasibility of providing precise navigation and positioning service for UAV with single frequency GPS/BDS receiver. The challenges of precise positioning for UAV with low cost receivers are threefold: (1) signal captured with low cost receivers and antennas has poorer quality and interference immunity. (2) UAV moves fast and flexible. (3) UAV navigation requires real time and high reliable positioning solution. GPS-based single frequency can provide centimeter accuracy positioning in friendly environments, while its availability and reliability is difficult to meet the requirement. In this study, we introduced GPS/BDS combined RTK positioning, which increases the redundancy number and improved the precision and reliability of float solution. Meanwhile, we analyzed the signal and antenna gain characteristics of low cost receiver and antenna, and established a refined stochastic model for GPS and BDS observations. We also made use of the Doppler observations to improve the kinematic model and quality control, which significantly improves the success rate of carrier phase ambiguity resolution in single frequency RTK case. In order to validate the performance of our algorithm, we carried out in-flight tests with Tersus single frequency GPS/BDS receiver and analyzed the test results. The results indicate that our RTK algorithm can improve the fix rate of ambiguity resolution from 36 % to around 60 % in challenging environments. We also validated that GPS/BDS RTK has better availability and reliability than GPS stand-alone RTK.