Light Detection and Ranging (LiDAR) based Simultaneous Localization and Mapping (SLAM) has drawn increasing interests in autonomous driving. However, LiDAR-SLAM suffers from accumulating errors which can be significantly mitigated by Global Navigation Satellite System (GNSS). Precise Point Positioning (PPP), an accurate GNSS operation mode independent of base stations, gains growing popularity in unmanned systems. Considering the features of the two technologies, LiDAR-SLAM and PPP, this paper proposes a SLAM system, namely P 3 -LOAM (PPP based LiDAR Odometry and Mapping) which couples LiDAR-SLAM and PPP. For better integration, we derive LiDAR-SLAM positioning covariance by using Singular Value Decomposition (SVD) Jacobian model, since SVD provides an explicit analytic solution of Iterative Closest Point (ICP), which is a key issue in LiDAR-SLAM. A novel method is then proposed to evaluate the estimated LiDAR-SLAM covariance.In addition, to increase the reliability of GNSS in urban canyon environment, we develop a LiDAR-SLAM assisted GNSS Receiver Autonomous Integrity Monitoring (RAIM) algorithm. Finally, we validate P 3 -LOAM with UrbanNav, a challenging public dataset in urban canyon environment. Comprehensive test results prove that, in terms of accuracy and availability, P 3 -LOAM outperforms benchmarks such as Single Point Positioning (SPP), PPP, LeGO-LOAM, SPP-LOAM, and the loosely coupled navigation system proposed by the publisher of UrbanNav.
This study aims to examine whether the presence of polymorphisms in TNF-α (rs361525 and rs1799724) and MTHFR (rs1476413 and rs9651118) genes is associated with the pathogenesis of cerebral palsy (CP). A total of 105 CP patients and 114 age-, gender-, and ethnicity-matched healthy controls were genotyped for the selected polymorphisms, using TaqMan allelic discrimination assay. Odds ratios (OR) and 95 % confidence intervals (CI) were determined to measure the strength of associations of TNF-α and MTHFR polymorphisms with CP. The proportion of subjects with the gestational age more than 37 weeks or asphyxia was much larger in cases compared with controls (gestational age 63.8 vs. 34.2 %; asphyxia 25.7 vs. 7.9 %). The genotype frequencies of TNF-α rs1799724 were similar between groups (P > 0.05), yet the allele distributions were significantly different (P < 0.05). Both the allele and genotype distributions of MTHFR rs9651118 polymorphism varied significantly between the groups (P < 0.05). Subgroup analysis based on gestational age indicated a significant association between rs361525 and rs9651118 and CP with or without premature. TNF-α protein concentrations were significantly increased among patients with rs361525 GG genotype compared with controls. Also, a significant increase in the risk of CP was observed to be associated with the interactions of TNF-α rs1799724 and MTHFR rs9651118 (OR 2.75, 95 % CI 1.23-6.13). These data suggest that polymorphisms in TNF-α and MTHFR genes might be involved in the pathogenesis of CP in Chinese infants.
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