Laser Scanning for Precise Ovalization Measurements: Standard Deviations and Smoothing Levels

• Published in: Journal of surveying engineering 2016-11, Vol.142 (4)
• Main Authors: Nuttens, Timothy, Stal, Cornelis, De Backer, Hans, Deruyter, Greta, Schotte, Ken, Van Bogaert, Philippe, De Wulf, and Alain
• Format: Article
• Language: English
• Subjects: Case Study; Lasers; Mathematical analysis; Monitoring; Optimization; Scanners; Scanning; Smoothing; Standard deviation
• ISSN: 0733-9453; 1943-5428
• DOI: 10.1061/(ASCE)SU.1943-5428.0000165

AbstractMonitoring of measurements needs to be supported by a thorough knowledge of the achievable accuracy of the measurement equipment and the processing methodology. This study on ovalization monitoring with laser scanning in tunnels under construction focused on fast-performing laser scanners and their achievable accuracy. This research also investigated the optimum smoothing level of the laser scanning data to achieve the best estimates of ovalization. The experimentally based standard deviations indicate that the used phase-based laser scanner delivers highly accurate results with standard deviations between 0.34 and 0.58 mm, depending on the applied smoothing level. In this research, this laser scanner was used, together with a [x – 0.008 rad; x + 0.008 rad] smoothing interval on the calculated radius values to meet the accuracy requirement requested by the client (0.5 mm), even when using multiple setups. Another used type of laser scanner (pulse-based) also delivers standard deviations around this range, but this instrument has a lower scanning speed and a smaller vertical field of view, making it less adapted for measurements in time-restricted tunnel-monitoring projects.