Xiong Lin, Wang Guoquan, Bao Yan, Zhou Xin, Wang Kuan, Liu Hanlin, Sun Xiaohan, Zhao Ruibin
Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX 77204, USA.
The Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China.
Sensors (Basel). 2019 Jul 24;19(15):3252. doi: 10.3390/s19153252.
Terrestrial laser scanning (TLS) has become a powerful data acquisition technique for high-resolution high-accuracy topographic and morphological studies. Conventional static TLS surveys require setting up numerous reflectors (tie points) in the field for point clouds registration and georeferencing. To reduce surveying time and simplify field operational tasks, we have developed a rapid TLS surveying method that requires only one reflector in the field. The method allows direct georeferencing of point clouds from individual scans to an East-North-Height (ENH) coordinate system tied to a stable geodetic reference frame. TLS datasets collected at a segment of the beach-dune-wetland area in Freeport, Texas, USA are used to evaluate the performance of the rapid surveying method by comparing with kinematic GPS measurements. The rapid surveying method uses two GPS units mounted on the scanner and a reflector for calculating the northing angle of the scanner's own coordinate system (SOCS). The Online Positioning User Service (OPUS) is recommended for GPS data processing. According to this study, OPUS Rapid-Static (OPUS-RS) solutions retain 1-2 cm root mean square (RMS) accuracy in the horizontal directions and 2-3 cm accuracy in the vertical direction for static observational sessions of approximately 30 min in the coastal region of Texas, USA. The rapid TLS surveys can achieve an elevation accuracy (RMS) of approximately 3-5 cm for georeferenced points and 2-3 cm for digital elevation models (DEMs). The elevation errors superimposed into the TLS surveying points roughly fit a normal distribution. The proposed TLS surveying method is particularly useful for morphological mapping over time in coastal regions, where strong wind and soft sand prohibit reflectors from remaining strictly stable for a long period. The theories and results presented in this paper are beneficial to researchers who frequently utilize TLS datasets in their research, but do not have opportunities to be involved in field data acquisition.
地面激光扫描（TLS）已成为一种用于高分辨率高精度地形和形态研究的强大数据采集技术。传统的静态TLS测量需要在野外设置大量反射器（控制点），用于点云配准和地理参考。为了减少测量时间并简化野外作业任务，我们开发了一种快速TLS测量方法，该方法在野外仅需一个反射器。该方法允许将单个扫描的点云直接地理参考到与稳定大地测量参考框架相关的东-北-高（ENH）坐标系。在美国得克萨斯州弗里波特的一段海滩-沙丘-湿地地区收集的TLS数据集，通过与动态GPS测量结果进行比较，用于评估快速测量方法的性能。快速测量方法使用安装在扫描仪上的两个GPS单元和一个反射器来计算扫描仪自身坐标系（SOCS）的北向角度。建议使用在线定位用户服务（OPUS）进行GPS数据处理。根据本研究，对于美国得克萨斯州沿海地区大约30分钟的静态观测时段，OPUS快速静态（OPUS-RS）解在水平方向上保持1-2厘米的均方根（RMS）精度，在垂直方向上保持2-3厘米的精度。快速TLS测量对于地理参考点可实现约3-5厘米的高程精度（RMS），对于数字高程模型（DEM）可实现2-3厘米的精度。叠加在TLS测量点上的高程误差大致符合正态分布。所提出的TLS测量方法对于沿海地区随时间的形态测绘特别有用，在沿海地区，强风和软沙使得反射器无法长时间严格保持稳定。本文提出的理论和结果对那些在研究中经常使用TLS数据集但没有机会参与野外数据采集的研究人员有益。
