3-D LiDAR-aided GNSS NLOS mitigation for reliable GNSS-RTK positioning in urban canyons

Abstract

Global navigation satellite system (GNSS) real-time kinematic (RTK) and light detection and ranging (LiDAR) odometry are complementary, offering global and local positioning capabilities, respectively. GNSS-RTK/LiDAR integration primarily focuses on two aspects: 1) 3-D LiDAR-aided (3DLA) GNSS nonline-of-sight (NLOS) mitigation using point cloud data and 2) state estimation via tightly coupled GNSS/LiDAR integration, which improves GNSS geometry, yielding better float solutions and lower estimation uncertainty. Combining 3DLA NLOS mitigation with tightly coupled integration can thus enhance urban positioning reliability. However, current 3DLA GNSS-RTK system remains limited in terms of NLOS detection reliability, tightly coupled integration effectiveness, and computational efficiency. This article proposes a tightly coupled GNSS-RTK/LiDAR/INS integration system with 3DLA NLOS mitigation. We focus on improving the robustness of 3DLA NLOS detection, the efficiency, and effectiveness of the tightly coupled GNSS-RTK/LiDAR integration. Evaluations on the challenging UrbanNav dataset show over 70% improvement in positioning accuracy compared to conventional GNSS-RTK, achieving submeter to meter-level precision. Runtime analysis confirms the system supports real-time optimization and ambiguity resolution (AR) with an average computation time of 70 ms.