直线特征约束下利用Plücker坐标描述的LiDAR点云无初值配准方法

A Linear Features-Constrained, Plücker Coordinates-Based, Closed-Form Registration Approach to Terrestrial LiDAR Point Clouds

  • 摘要: 经典的基于点状特征匹配的地面激光雷达(light detection and ranging,LiDAR)点云配准算法实现过程中,点状特征的提取精度对算法运行结果的影响通常较大;基于迭代运算的LiDAR点云配准算法计算量大,对未知参数的初值依赖程度较高,在求解大转角刚体变换参数时算法不稳定。对此,提出了一种线状特征约束下基于Plücker直线坐标描述的LiDAR点云配准算法。立足于经典的向量代数与对偶四元数的相关理论与方法,分析并确定了Plücker直线坐标与对偶四元数之间的相互转换关系以及模型描述方法;以LiDAR点云配准前后同名线状特征的Plücker直线坐标相等为约束条件,构建了线状特征约束下基于Plücker直线坐标描述的刚体变换模型;立足于最小二乘基本准则,通过目标函数的极值化分析实现了线状特征约束下地面LiDAR点云配准参数的直接求解。实验结果表明,所构建的基于Plücker直线坐标描述的地面LiDAR点云配准模型,无需事先确定变换参数的初值,避免了多元函数的线性化过程,解除了参数结果对于迭代初值的依赖,理论上克服了迭代法在求解大转角相似变换参数时的算法不稳定问题。此外,较之单纯基于点状特征匹配的LiDAR点云配准算法,该算法可以有效地增强LiDAR点云配准过程的约束,达到提高配准质量的目的。

     

    Abstract: Considering that the low accuracy of extracted point features may affect the seamless fusion of point clouds from two neighbor stations, and by using traditional iterative-form solutions to implement point clouds registration, the large amount of computer resources, the high dependence on initial values of unknown parameters, and its theoretical instability in solving transformation parameters for large-angle registration can hardly be neglected. To alleviate the above problems, a linear features-based, closed-form solution to registration of pairwise terrestrial LiDAR point clouds is proposed, in which Plücker coordinates is introduced to represent linear features in 3D space. A Plücker coordinate-based object function is first introduced on the assumption of the consistency of each conjugate linear features from the two neighbor stations after registration. Based on the theory of least squares and by extreme value analysis of the error norm, detailed derivations of the model and the main formulas are all given. Experiments show that the proposed algorithm is just the one expected, the linearization of multivariate function is neglected in the implementation, and it runs well without initial estimates of unknown parameters, which assures the stability in solving transformation parameters for large-angle registration problems. Furthermore, by employing linear features as registration primitives, random errors may be greatly decreased by fitting contrast to point features based registration algorithms.

     

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