Terrestrial laser scanning and continuous wavelet transform for controlling surface flatness in construction - A first investigation

We propose a novel approach to surface flatness characterization in construction that relies on the combination of Terrestrial Laser Scanning (TLS) and the Continuous Wavelet Transform (CWT). The former has the advantage over existing measurement technologies of providing both accurate and extremely dense measurement over surfaces. The latter provides the means to conduct frequency analysis with high resolution in both the space and frequency domains. This novel approach is tested using two real concrete floors and the results compared with those obtained with the Waviness Index method. The results show a high level of correlation. In fact, the proposed approach delivers a higher level of precision in the frequency and spatial domains. We also show what seems to be a weakness of the Waviness Index method in the detection of undulation with short periods. Finally, although not experimentally demonstrated here, the proposed method has the very interesting additional advantage of being applicable in 2D, that is over an entire surface instead of sampled survey lines (1D).