Front end 3 Optical radar 3 Robotics 3 Simultaneous localization and mapping 3 Simultaneous localization and mapping algorithms Degrees of freedom (mechanics) 2 IMU 2 Iterative methods 2 Kalman filters 2 LiDAR 2 Perceptually degraded scene 2 Performance 2 SLAM 2 Six degrees of freedom 2 State estimation 2 Tightly-coupled 2 Underground tunnels 2 perceptually degraded scenes 2 state estimation 2 2D lidar 1 2d lidar 1 Complex environments 1 Localization method 1 Mapping 1 Mapping method 1 Multi-sensor fusion 1 Scan-matching 1 Two-dimensional 1 multi-sensor fusion 1 simultaneous localization and mapping 1