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Laser SLAM enables to locate the vehicle itself even in an unknown environment, and to efficiently sample the three-dimensional geospatial information of the traversed environment, which has been drawn wide attention in the field of autonomous driving in recent years. To improve the accuracy and performance of the laser SLAM system in a point cloud degenerated tunnel environment, we present an intensity enhanced laser SLAM approach based on LOAM. First, we improve the feature extraction module of LOAM. An adaptive feature extraction method based on spherical projection image is presented to extract line, façde, ground and reflectors from a single laser sweep. Besides, to solve the issue on point cloud registration degeneracy in tunnel environments, we presented intensity feature-basedregistration approach to fix the vehicle pose resulting from the geometric feature-based registration error. Reflecting features in the surrounding are adaptively extracted to ensure the adaptivity of our improved laser SLAM approach. The experimental results show that the proposed method presented the better and more robust performance especially in degenerated environments, e.g., long straight tunnel, comparing with the performance of LOAM and HDL-Graph-SLAM. The accuracy of the proposed method was an order of magnitude larger than that of LOAM and HDL-Graph-SLAM.

With the construction of big science projects in China, the precise engineering surveying technology developed rapidly in the 21th century. Firstly, the paper summarized up the current development situation for the precise engineering surveying instrument and theory. Then the three typical cases of the precise engineering surveying practice such as accelerator alignment, industry measurement and high-speed railway surveying technology are focused.

At present, the number of orbit satellites is limited for the Beidou satellite navigation system. In special terrain like “city Canyon” and other special circumstances, the signal of Beidou is easy to be blocked, which reduces positioning accuracy or interrupts positioning continuity of users. Joining pseudolites can effectively solve the problem of the insufficient number of BeiDou satellites visible to users. During cooperative positioning of Beidou satellites and pseudolites, the multi-path problem in pseudo-range observation values of the BeiDou satellite and the pseudolite shall be properly handled to obtain better positioning accuracy. The CNMC method (Code Noise and Multi-path Correction) can effectively reduce the multi-path effect of the BeiDou satellite's pseudo-range observation value, but cannot be applied directly to pseudo-range data processing of the pseudolite due to different observation error characteristics caused by different signal propagation paths. To solve the multi-path processing problem of pseudolites, the CNMC method is improved in this paper. The BeiDou/Pseudolite dynamic cooperative positioning experiments were conducted in the actual field of pseudolites. The test results show that the three-dimensional positioning accuracy is increased from 2.326 m to 1.936 m with enhanced positioning stability after pseudo-range observation values of the BeiDou satellite and the ground pseudolite are processed by the CNMC method.