Characterization of geotechnical and geological features with time-lapse infrared thermography and geo-spatial technologies—a case study

Abstract This paper presents a case study adopting a proposed methodological framework combining non-contact and non-destructive inspection techniques, including time-lapse infrared thermography (IRT) and unmanned aerial system (UAS), to study a natural terrain landslide that occurred in Sai Wan of Hong Kong. Time-lapse IRT was adopted since traditional snapshot IRT only focuses on single thermal images without considering the time factor in a continuous IRT survey. Natural logarithmic and linear regression fitting were applied to the temperature values in a series of thermal images collected within a period. Then the thermal decay gradient of each pixel was calculated and used to form a visualization of the target region, i.e., thermal decay map. Based on the thermal decay map, segmentation was applied based on the distributions of clusters (in which the thermal decay gradient values ranged from − 0.125 to 0.01) in the histogram of the thermal decay map. The resulting segmentation map can be used to highlight vegetation, fractures and joints, and seepage in the selected site without considering the absolute value of surface temperature. The result from this paper provides a proof of concept of the proposed approach in a single site, which the approach shows the potential in improving and facilitating feature identification and quantitative zoning in secondary landslide hazard inspection.