Ultra-wideband (UWB) technology has been widely used for indoor positioning of UAVs due to its excellent range performance. The traditional UWB positioning system requires at least three anchors to complete 3D positioning. Reducing the number of anchors further means reducing the cost and difficulty of deployment. Therefore, this paper proposes a positioning model using only two anchors. In this model, the altitude of the UAV is measured by a rangefinder. Then, the position of the UAV is projected onto the horizontal plane, converting 3D positioning into 2D positioning. The rangefinder's range accuracy is higher than that of the UWB, which is beneficial for improving 3D positioning accuracy. In addition, an altitude fusion method of integrating rangefinder and barometer data is designed to realize the switching of altitude data and barometer calibration to solve the problem of obstacles under the UAV affecting the altitude measurement. On this basis, the multi-sensor data fusion algorithm based on a dual-anchor positioning model is designed to improve positioning accuracy, and the data of the UWB, rangefinder, barometer, and accelerometer are fused by the unscented Kalman filter (UKF) algorithm. The positioning simulation and experiment show that the positioning accuracy of the dual-anchor model is generally higher than that of the three-anchor model, with decimeter-level positioning accuracy.
