Lidar Intensity as a Remote Sensor of Rock Properties

Abstract

Abstract Lidar collects high-resolution spatial data, making it a popular tool for outcrop investigations; however, few of these studies utilize lidar’s spectral capability. Lidar scanners commonly collect intensity returns (power returned/power emitted) that are influenced primarily by distance and target reflectivity, with lesser influence from angle of incidence, roughness, and environmental conditions. Application of distance normalization results in values that approximate target reflectivity. At the near-infrared wavelength of lidar, quartz-rich sandstones are more reflective than clay-rich mudstones. Scans of unweathered core and weathered outcrop were collected to investigate the relationship between lithology and lidar intensity. In unweathered, laboratory samples, intensity shows an inverse relationship to wt. % clay and are positively correlated to wt. % combined quartz, plagioclase, and K-feldspar. A similar relationship was also observed in scans of lightly weathered outcrop, although weathering and moisture diminished intensity contrast between sand-rich and shale-rich intervals. Thus, lidar intensity is a possible remote sensor of lithology, particularly in remotely located and inaccessible outcrops.