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Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

bjectives: Pose estimation of light detection and ranging (LiDAR) simultaneous localization and mapping (SLAM) relies on scan matching algorithm with high accuracy and reliability. Methods: Based on the iterative closest point (ICP) algorithm in LiDAR odometry and mapping (LOAM), we propose a re⁃ silient real-time LiDAR SLAM algorithm where the normal distributions transform (NDT) is flexibly se⁃ lected according to a so-called environmental feature value (EFV) for identifying unstructured scenes. Re⁃ sults: Experimental results show that the EFV can effectively distinguish unstructured scenes, and the de⁃ bugging method of EFV threshold is given. The analysis of localization and mapping experiments show that compared with the classic LiDAR SLAM algorithms such as LOAM, the proposed algorithm has a great improvement in accuracy and reliability, of which the outdoor accuracy can be obtained from meter level to decimeter level. Moreover, the method can build a map and obtain a global consistent map when facing handheld data. Conclusions: Therefore, the proposed method has good environmental adaptability, thus enriching and developing the SLAM method for complex environments. [ABSTRACT FROM AUTHOR]

Objectives: With the rapid popularization of low-cost receivers, single-frequency global navigation satellite system (GNSS) is now widely used. The cycle slip rate of a single-frequency GNSS receiver is commonly high in a complex situation. Although geometry-free (GF) model can detect some large cycle slips, it is not sensitive to small cycle slips. The geometry-based (GB) model is efficient for cycle slip detection and repair, but its success rate of detection descends correspondingly with an excessive number of abnormal satellites. Methods: By combining the advantages of GF and GB models, this paper proposes a new cycle slip detection and repair method. The proposed method firstly detects and rejects the abnormal satellites with large cycle slips by GF model, then uses GB model to detect small cycle slips and repair large cycle slips. Results: The results show that the proposed cycle slip detection and repair method can enhance the success rate if many cycle slips occur simultaneously. The success rate can be improved by approximately 50% even when the abnormal satellites reach the half or more of total numbers simultaneously. Conclusions: Compared with the traditional GB model, the proposed GF+GB model can take advantage of each model to improve the performance when multi-cycles occur. [ABSTRACT FROM AUTHOR]

Objectives: Differential code bias (DCB) is one of the important factors affecting the accuracy of ionospheric monitoring and high-precision positioning. The establishment of DCB correction model is of great significance for high-precision positioning. Methods: Aiming at the problem that the BDS-3 satellite clock time references of broadcast ephemeris and precise ephemeris are not uniform, firstly, we introduce the DCB estimation methods of Chinese Academy of Sciences (CAS) and German Aerospace Center (DLR), and give the accuracy evaluation and analysis results of some DCB products. Secondly, the DCB correction models of BDS-3 single-frequency and dual-frequency standard point positioning (SPP), dual frequency precise point positioning (PPP) are proposed. Finally, both SPP and PPP experiments are carried out with different schemes by using five-day measured data of the multi-GNSS experiments (MGEX) stations. Results: The results show that the MGEX DCB products have high stability. And the accuracies of single-frequency and dual-frequency SPP are increased by 48%—85% and 71%—91% after using DCB correction, respectively. The convergence time of dual-frequency static PPP is reduced by 56%—83% after using DCB correction. Conclusions: It can be concluded that the satellite DCB correction can improve the SPP positioning accuracy and reduce the PPP convergence time. [ABSTRACT FROM AUTHOR]

All observations inevitably contain outliers. Outlier detection is a particularly tough problem under the complex conditions of the combination of multi-frequency and multi-constellation and urban canyon environments. Here, outlier detection is studied to ensure accurate and reliable positioning performance of BDS/GNSS data. The outlier detection schemes with different thresholds were proposed based on mean shift and variance inflation. Then dedicated experiments under complex conditions were carried out to evaluate the performance of the proposed outlier detection schemes. The experimental results show that the RMSE of the mean shift based small threshold (U1/2α2 (0, 1) ) scheme is improved by 0.059 m,0.017 m, and 0.062 m in the E, N, and U directions, respectively. The RMSE of the combined large iterative threshold (w) and small threshold (k0, k1) scheme based on variance inflation is improved by 0. 098 m,0.055 m, and 0. 209 m in the E, N, and U directions, respectively. The results show that the above two schemes can detect and identify outliers under complex conditions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)