*Article* **LiDAR-Visual-Inertial Odometry Based on Optimized Visual Point-Line Features**

**Xuan He 1,2, Wang Gao 1,2,\*, Chuanzhen Sheng 3,4, Ziteng Zhang 3,4, Shuguo Pan 1,2, Lijin Duan 5, Hui Zhang 1,2 and Xinyu Lu 1,2**


**Abstract:** This study presents a LiDAR-Visual-Inertial Odometry (LVIO) based on optimized visual point-line features, which can effectively compensate for the limitations of a single sensor in real-time localization and mapping. Firstly, an improved line feature extraction in scale space and constraint matching strategy, using the least square method, is proposed to provide a richer visual feature for the front-end of LVIO. Secondly, multi-frame LiDAR point clouds were projected into the visual frame for feature depth correlation. Thirdly, the initial estimation results of Visual-Inertial Odometry (VIO) were carried out to optimize the scanning matching accuracy of LiDAR. Finally, a factor graph based on Bayesian network is proposed to build the LVIO fusion system, in which GNSS factor and loop factor are introduced to constrain LVIO globally. The evaluations on indoor and outdoor datasets show that the proposed algorithm is superior to other state-of-the-art algorithms in real-time efficiency, positioning accuracy, and mapping effect. Specifically, the average RMSE of absolute trajectory in the indoor environment is 0.075 m and that in the outdoor environment is 3.77 m. These experimental results can prove that the proposed algorithm can effectively solve the problem of line feature mismatching and the accumulated error of local sensors in mobile carrier positioning.

**Keywords:** multi-sensor fusion; visual point and line feature; SLAM; LiDAR-visual-inertial odometry
