Precise 3D extraction of building roofs by fusion of UAV-based thermal and visible images

Abstract

Thermography is an efficient way of detecting the thermal problems of the roof as a major part of a building's energy dissipation. Thermal images have a low spatial resolution, making it a challenge to produce a three-dimensional thermal model using aerial images. This paper proposes a combination of thermal and visible point clouds to generate a higher-resolution thermal point cloud from roofs of buildings. For this purpose, after obtaining the internal orientation parameters through camera calibration, visible and thermal point clouds were generated and then registered to each other using ground control points. The roofs of buildings were then extracted from the visible point cloud in four steps. First ground points were removed using cloth simulation filter (CSF), and then vegetation points were eliminated by applying entropy and redgreen-blue vegetation index (RGBVI). Geometric features and a segmentation step were considered to filter roofs from other parts. Finally, by combining visible and thermal point clouds, the generated point had a high spatial resolution along with thermal information. In the achieved results, the thermal camera calibration was performed with an accuracy of 0.31 pixels, and the thermal and visible point clouds were registered with an absolute distance of < 0.3 m. The experimental results showed an accuracy of 18 cm for automated extraction of building roofs and 0.6 pixel for production of a high-resolution thermal point cloud, which was five times the density of the primary thermal point cloud and free from distortions.

High-Resolution Real-Time Coastline Detection Using GNSS RTK, Optical, and Thermal SfM Photogrammetric Data in the Po River Delta, Italy

“…The applications of these sensors on drones are available for the detection of peat fires [26], wildlife detections and monitoring [27,28], building audits, forest monitoring [29], agriculture parameters estimations [30], etc. Due to the general low resolution of thermal images, thermal and optical images can be combined to generate higher-resolution and high-quality thermal mapping models [31,32]. These data, easily acquired by low-cost drones, can also find applications in the definition and monitoring of the coastline.…”

Fast and Accurate Registration of Terrestrial Point Clouds Using a Planar Approximation of Roof Features

“…The process terminates when no roof ridges can be detected. Dahaghin et al in [29] proposed a method to extract building roofs from the visible point cloud. The method includes ground filtering, vegetation removal, wall removal based on geometric properties, and, finally, segmentation of remaining points.…”

Evaluation of the Potential of Aerial Thermal Imagery to Generate 3d Point Clouds

“…Today, aerial thermal images obtained from unmanned platforms are used in many fields: from managing water resources and forest health monitoring to discovering and tracking objects on the surface of the oceans and discovering and tracking pedestrians and vehicles, building energy modeling and similar applications (Leira et al, 2015, Smigaj et al, 2015, Ma et al, 2016, Cho et al, 2015. Furthermore, fusing thermal and visible imageries has been investigated in order to precise 3D extraction of building roofs (Dahaghin et al, 2021). In many of these applications, thermal data have been obtained with the help of unmanned aerial platforms.…”