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Compared with traditional methods, the three-dimensional laser-scanning (3D-LS) technique can efficiently acquire many high-quality geometric properties of rock discontinuities. In practice, engineers usually prefer to simplify the processing by using single-station point data and roughly orienting owing to the complexity of registration/georeferencing multi-station point data. However, prior published studies have paid little attention to the accuracy and reliability when determining discontinuity orientations using 3D-LS. We propose a reliable and accurate method with robust on-site applicability. As part of an ongoing effort, we are evaluating the precision of the commonly used coarse registration method and the fine registration method, and promoted the optimized coarse- and fine-registration methods and evaluated their precision. It is found that: (1) the common and the optimized registration method can meet our project's engineering requirements, and the optimized registration method improved accuracy in the dip direction by approximately 1°; (2) fine registration using an iterative closest point (ICP) algorithm can correct both dip direction and dip angle; and (3) the orientation is of high precision with commonly used coarse and fine registration, whereas the optimization effect to correct the orientation is slightly limited. [ABSTRACT FROM AUTHOR]

With the aid of three-dimensional laser scanning (3D-LS), a lot of geometric properties of rock discontinuities can be derived from the point cloud data. Due to the complexity of registration and georeferencing of multi-station point data, geological engineers tend to simplify processing by using single-station point data and orienting coarsely. However, there is a lack of accuracy and reliability study in the identification of discontinuity orientations with 3D-LS using different registration/georeferencing modes. In this study, the single-station scanning without registration/georeferencing was applied first to examine the accuracy and reliability of the scanner's built-in direction system. After that, two types of automated registration/georeferencing modes were examined for the accuracy in rock mass discontinuity analysis. The results show that the dip angle measured by the scanner's built-in directional system is reliable, accurate and can meet engineering requirements, while the dip direction measured by the scanner's built-in directional system is unreliable and inaccurate. The dip direction is consistent but inaccurate through the semi-automated registration using natural point features and georeferencing by the scanner's built-in directional system. Only through real-time kinematic (RTK) registration/georeferencing can the dip direction be reliable and accurate. It is observed that orientations captured by 3D-LS can be more accurate with RTK registration/georeferencing than manual survey. [ABSTRACT FROM AUTHOR]