Calibration of Laser Scanners

地面激光扫描仪(TLS)的精度受到内部扫描仪不对准(校准参数)的影响，其大小大多超过随机偏差。在形变分析的背景下，这主要有两个结果：一方面，两个时期的测量值之间的差异d被系统偏差所抵消。另一方面，系统偏差以类似的方式影响相邻点，这导致需要纳入随机模型Σ_dd的测量值之间的相关性。为了保证变形分析的无偏性，必须对系统偏差进行校准。因此，作为整个研究单位和项目的一部分，该项目的目标是减少系统偏差，以获得无偏点云差异d，并为扫描仪Σ_cc的校准参数推导出完全填充的方差-协方差矩阵，这是Σ_dd的重要部分。TLS校准程序的进一步发展是基于无偏激光扫描仪的变形分析的关键之一，该分析旨在检测微小的几何变化。也就是说，对于本研究单位提案中提出的几点而言，校准具有很高的相关性：a)不考虑系统偏差导致的数据中可能产生表面表示偏差的伪影；b)消除与仪器相关的系统偏差增加灵敏度；c)正确量化校准不确定度对于全面的测量不确定度估计是必要的；d)正确的系统误差函数模型对于无偏见地规划最佳仪器定位是必要的。

The accuracy of terrestrial laser scanners (TLS) is mitigated by internal scanner misalignments (calibration parameters) whose magnitude mostly exceeds the one of random deviations. This has mainly two consequences in the context of a deformation analysis: On the one hand, the differences d between the measurements at two epochs are biased by the systematic deviations. On the other hand, systematic deviations affect adjacent points in a similar way, which causes correlations between the measurements that need to be incorporated into the stochastic model Σ_dd. To guarantee an unbiased deformation analysis, the systematic deviations must be calibrated. Thus, the goal of this project as part of the whole research unit with the projects is to - reduce systematic deviations to get unbiased point cloud differences d - and to derive a fully populated variance-covariance matrix for the calibration parameters of the scanner Σ_cc, that is an essential part of Σ_dd. A further development of TLS calibration procedures is one of the linchpins for the unbiased laser scanner-based deformation analysis that aims at detecting small geometric changes. Namely, the calibration is of high relevance for several points raised in this proposal for a research unit: a) not-accounting for systematic deviations causing artifacts in data that can bias the surface representation; b) removing instrument-related systematic deviations increases the sensitivity; c) correct quantification of the calibration uncertainty is necessary for the comprehensive measurement uncertainty estimation; d) a correct functional model of systematic errors is necessary for unbiased planning of optimal instrument positioning.