Airborne combined photogrammetry—infrared thermography applied to landslide remote monitoring

Abstract

The combination between two remote surveying methods is presented herein as a pioneering approach for landslide airborne monitoring. The survey of an active landslide by UAV-based RGB photogrammetry and infrared thermography, sided by the knowledge of the field condition, allowed increasing the scientific experience on the remote sensing of slope instability phenomena by analyzing multiple aspects related to the evolution of key slope features. In this research, the state and distribution of activity of a landslide was monitored by matching data arising from three-dimensional models of the slope, built by exploiting the aerial RGB photogrammetric technology, and thermal outcomes, resulting from the airborne application of infrared thermography principles. In this frame, thermal anomalies detected during different monitoring campaigns allowed recognizing peculiar features along the unstable slope that could be related to specific kinematic elements involved in the landslide activity. Forming cracks, developing scarps, wet terrain portions, and loose material are some of the elements that could be located by integrating thermal outcomes with Digital Surface Models of the slope. Thanks to the different thermal behavior of such elements, strengthened herein by a novel approach of thermal data processing (i.e. the study of thermal slope profiles), the lateral and retrogressive evolution of the studied movement was first hypothesized and then verified in field. Achieved results show that the location of thermal anomalies well corresponds to field structures, which sometimes are hardly detectable by in situ or RGB surveys, thus suggesting the high potential of the methodological approach developed for this study. The scientific validity of presented data gains relevance thanks to the positive field validation. This paves the way to further studies aimed at implementing the infrared aerial survey of landslides, which surely could bring benefits to practical applications in terms of survey speed and spatial coverage, especially in areas characterized by bad field logistics.

Unmanned Aerial Vehicles (UAVs) in Landslide Investigation and Monitoring: A Review

“…As any object with a temperature higher than absolute zero emits electromagnetic radiation within the infrared (IR) band, known as "thermal radiation", an IR thermal camera is a novel operational tool for monitoring cracks on unstable landslides [48,49,57,58]. As shown in Figure 9, Vivaldi et al (2022) [134] introduces an approach to landslide monitoring using UAV-based infrared thermography. Through the integration of three-dimensional models generated from aerial RGB photogrammetry and thermal outcomes from infrared thermography, the research successfully monitors the state and distribution of landslide activity, detecting features such as forming cracks, scarps, wet terrain portions and loose material.…”

A Feasibility Study of Thermal Infrared Imaging for Monitoring Natural Terrain—A Case Study in Hong Kong

“…However, data collection in these studies was conducted separately by UAV and ground-based IRT, which did not fully utilize the potential of combining a UAV and IRT. Landslide remote monitoring which adopted a UAV system equipped with a thermal camera was performed by [32], which used snapshot thermal data collected using a UAV to monitor the landslide area. The results proved that with the help of IRT, certain features including landslide crown and head, man-made objects (groove and pile wall), reinforced soil, and wet terrain could be successfully identified.…”

Multi-source remote sensing-based landslide investigation: the case of the August 7, 2020, Gokseong landslide in South Korea

“…In addition, monitoring using satellite radio detection and ranging (radar) enables observation of tiny displacements at the millimeter scale and can also observe past displacement histories. Therefore, the remote sensing techniques are widely utilized not only in the field of landslide disasters but also in various geo-science fields which requires long-term monitoring over a large area 19 – 26 .…”