Infrared thermal dense point clouds: A new frontier for remote landslide investigation

Abstract

A novel way of analysing IRT images of landslides using thermal dense point clouds is herein presented. The Infrared Thermo Point Cloud tool was specifically developed to adjust and homogenize the temperature range of input images prior to the realization of a dense point cloud through conventional algorithms. In this way, bias and errors arising from differences in the temperature ranges of overlapping thermograms were avoided and a three-dimensional thermal model of landslides, holding both spatial and temperature information, was achieved. The possibility of analysing thermal IR data in the third dimension allowed a better interpretation of thermal anomalies that could be, therefore, reliably linked to the slope morphology. The analysis of thermal dense point cloud is herein commented with reference to two case studies, that involve different types of landslides. Achieved results show that the 3D thermal analysis is useful to highlight and locate open cracks, local discontinuity persistence, undercutting features and presence of moisture. These represent key elements, hardly detectable by the naked eye, which must be taken into account during a landslide analysis, especially in the frame of movement evolution assessment. The thermal analysis allowed also detecting anomalies that well match with structural plane traces. These can be also measured in space through a combined IRT-RGB joint model analysis. Moreover, thermal contrasts occurring along slopes affected by multiple landslides were exploited to map the different movements together with their main morphological elements. Results presented in this paper testify how the technological development and model implementation are fundamental to enhance and speed up the study of slope instability and mass movement by close range surveying procedures.