Automation of Thermographic 3D Modelling through Image Fusion and Image Matching Techniques

Abstract

Infrared thermography has proved to be an adequate technique for building inspection, as it can be used to determine energy efficiency through the measurement of heat losses, air leaks and infiltrations, and also to detect humidity areas. These parameters have great influence in energy consumption of buildings and in their users' well-being, which is demonstrated by the appearance of regulations as the Directive 2002/91/CE about Energy Efficiency.Geometry and spatial relationships are very important in building inspection because they make location of thermal defects possible. Moreover, quantification of heat losses is not possible without measuring the area affected. As plans are not always available or updated, especially in the case of old buildings, the metric survey is essential when developing an energetic study. Metric documentation in old buildings is hindered due to their complex and irregular geometry; therefore, geomatic techniques are an appropriate solution to achieve an accurate geometric data acquisition of buildings and 3D models.A procedure to fuse infrared and visible images in order to combine geometric information from photographies with thermal data from thermographies in the same image automatically is described in this paper. Fused images are then used for the automatic generation of a thermographic 3D model of the building through image matching. The proposed methodology is suitable for building inspection, where working space and time are usually limited so a reduction on the number and size of instruments is appreciated. Furthermore, automation of the process diminishes the error in results by avoiding operator's influence.

Understanding the Role of Thermography in Energy Auditing

“…Recent automated thermography efforts have focused on two areas ( Figure 2): transforming thermal images into 3D-reconstructions of buildings (e.g., [17,20,29,31,38]) and employing robots and vehicles to scale up data collection (e.g., [6,10,13,30,34,35,41]). Researchers argue that traditional 2D thermal images: (i) do not include geometry and spatial relationships, which are important for interpreting thermography [20,29]; (ii) are unordered, messy, and difficult to organize [17,20]; (iii) and require time-consuming and labor intensive post-hoc analysis [17,20,38].…”

“…Researchers argue that traditional 2D thermal images: (i) do not include geometry and spatial relationships, which are important for interpreting thermography [20,29]; (ii) are unordered, messy, and difficult to organize [17,20]; (iii) and require time-consuming and labor intensive post-hoc analysis [17,20,38]. Thermographic 3D reconstruction is cast as a solution to these problems and as a means of enabling better modeling that should reduce auditor error and subjectivity [17,29].…”

“…Researchers have primarily explored technical approaches for automatically transforming thermal images into higher fidelity 3D representations of buildings [17,20,29,31,38] and employing robots for data collection [6,10,13,30,35,41]. However, user studies of these tools have not been performed.…”

Automatic thermographic scanning with the creation of 3D panoramic views of buildings

“…During the design stage, numerical simulations are deployed both for new constructions and for the retrofit of existing buildings, while thermographic scans could be applied as a boundary conditions or as reference to verify the accuracy of fluid dynamics models 22 . The acquisition of thermal images could be coupled also with laser scanning or photographs, that create a two or three-dimensional model of the building 23 . This enhances the reliability of the geometrical model and improves significantly the intelligibility of the thermal data.…”

Aerial oblique thermographic imagery for the generation of building 3D models to complement Geographic Information Systems

“…In recent years, geometrical information obtained from external sources such as laser scanners has been combined with thermographic data in order to locate and measure these construction defects accurately [1,2]. Another option is the application of photogrammetric principles to the measurement of geometry directly from thermographies [3,4], or from a combination of visible and thermographic images looking for an improvement in the geometric resolution [5,6]. All these studies are performed with images acquired from the ground by an operator, consequently missing information of parts of the building that are essential for the complete understanding of its thermal behavior, as the roof.…”