Grain Size Distribution Analysis from 3D Laser Scan Data

The goal of this project was to see if information on the grain size distribution of a patch of cobbles could be obtained from the digital terrain model constructed from a laser scan of the cobble surface. The grain size distribution was to be extracted from the laser scans by the use of semivariograms. This was inspired by the research done by Hodge et al. (2009), who did the same. The results were compared to the results found by Hodge et al. (2009). In order to investigate getting information on GSD from laser scans properly, two different patches were made. Then the sizes of the cobbles were measured manually, in order to check the results from the future semivariograms. After that, both line laser scans were made and a 3D scan was made. Due to time constraints and experimental limitations, only one cobble surface was line scanned, and only one (the other) surface was 3D laser scanned. After all, only the line laser scans were processed. Then semivariograms were produced. It was found that if the manually measured data were compared with the variograms, correlations could be found for lags which corresponded to the grain sizes. But actual distinct fractal ranges couldn’t be seen. So, the use of only variograms (so without the manually measured data) is too ambiguous to be reliable. This result corresponded to the results from Hodge et al, who also could see the multifractal behavior of the cobbles, but not the distinct ranges.Ngan-Tillard D.Geo-EngineeringCivil Engineering and Geoscience