Quantifying Soil Structure from Field Excavation Walls using Multistripe Laser Triangulation Scanning

Soil structure is fundamental for understanding pedogenic, hydrological, and environmental processes, and its quantitative characterization is essential for advancing our understanding of soils. Despite this importance, structure quantification at scales relevant to field-based investigations has remained elusive. In this study, multistripe laser triangulation (MLT) scanning was investigated as a method for quantifying soil structure from excavation walls. An exposed soil profile in a Grundy soil series (fine, smectitic, mesic, Oxyaquic Vertic Argiudoll) was scanned using a commercially available MLT scanner. The field of view (FOV) for each scan overlapped adjacent FOVs in the vertical and horizontal directions. Data of interest from the MLT scans were areas where laser stripes were undetected by the scanner. These surface scan gaps (SSGs) outline structural units. We discovered that the angle between the scanner and excavation wall produces significant differences in the resulting data. Observed SSGs best represented structure outlines on the left side of the scan data FOVs. Several metrics describing SSG shape, size, and orientation were produced. Surface scan gap density, SSG fraction, relative surface area, and average unit size (i.e., size of areas outlined by SSGs) were related to soil structure described in the field. Average unit size compared well to the size classes from a traditional morphological description, and SSG orientation corresponded to structure type. Multistripe laser triangulation scanning holds potential for quantitative characterization of soil structure with implications for water flux modeling and advancing understanding of pedological and hydrological processes.