Investigating the use of LiDAR scanning as a method for the measurement of timber distortion features

[摘要] Measuring the extent to which a piece of structural timber has distorted at amacroscopic scale is fundamental to assessing its viability as a structuralcomponent. From the sawmill to the construction site, as structural timberdries, distortion can render it unsuitable for its intended purposes. This rejection of unusable timber is a considerable source of waste to the timberindustry and the wider construction sector. As such, ensuring accurate measurement of distortion is a key step in addressing ineffciencies within timber processing.Currently, the FRITS frame method is the established approach used togain an understanding of timber surface profile. The method, while reliable,is dependent upon relatively few measurements taken across a limited area of the overall surface, with a great deal of interpolation required. Further, theprocess is unavoidably slow and cumbersome, the immobile scanning equipment limiting where and when measurements can be taken and constricting the process as a whole.This thesis seeks to introduce LiDAR scanning as a new, alternative approachto distortion feature measurement. In its infancy as a measurementtechnique within timber research, the practicalities of using LiDAR scanningas a measurement method are herein demonstrated, exploiting many of theadvantages the technology has over current approaches. LiDAR scanning creates a much more comprehensive image of a timber surface, generating input data multiple magnitudes larger than that of the FRITS frame. Set-up and scanning time for LiDAR is also much quicker and more flexible than existing methods. With LiDAR scanning the measurement process is freed from many of the constraints of the FRITS frame and can be done in almost any environment.For this thesis, surface scans were carried out on seven Sitka spruce samplesof dimensions 48.5x102x3000mm using both the FRITS frame and LiDARscanner. The samples used presented marked levels of distortion and wererelatively free from knots. A computational measurement model was createdto extract feature measurements from the raw LiDAR data, enabling an assessment of each piece of timber to be carried out in accordance with existing standards. Assessment of distortion features focused primarily on the measurement of twist due to its strong prevalence in spruce and the considerable concern it generates within the construction industry. Additional measurements of surface inclination and bow were also made with each method to further establish LiDAR's credentials as a viable alternative.Overall, feature measurements as generated by the new LiDAR method compared well with those of the established FRITS method. From these investigations recommendations were made to address inadequacies within existing measurement standards, namely their reliance on generalised and interpretative descriptions of distortion. The potential for further uses of LiDAR scanning within timber researches was also discussed.

[发布机构] University:University of Glasgow;Department:School of Engineering

[关键词] Timber, distortion, LiDAR, FRITS Frame.