Laser scanning and the continuous wavelet transform for flatness control

Abstract

Current methods for surface flatness control in construction are based on sparse measurements and therefore may lead to inaccurate and imprecise results. Previous research has shown that Terrestrial Laser Scanning (TLS), with the accuracy and density of 3D point clouds it can provide, could support more complete and reliable control of surface flatness in construction. However, these previous works have only applied to existing methods based on sparse measurements, or used defect detection methods that are not based on the analysis of surface waviness (i.e. The frequencies in the floor surface profile), although this generally constitutes the key information sought after in surface flatness assessment. In this paper, we investigate the application of a frequency analysis technique, more particularly the Continuous Wavelet Trans-form (CWT), to TLS point clouds associated to surfaces. The aim is to make full use of the density of points provided by TLS and provide detailed results frequency-wise. We provide the reasoning behind employing the CWT for analyzing frequencies in this context, and report results obtained using data acquired from actual slabs. The CWT results are also compared with those obtained when applying the Waviness Index method. The encouraging preliminary results lead us to suggest a path forward for future development and testing with a view on possibly establishing a new standard test method for floor flatness.