Pixel-by-pixel rectification of urban perspective thermography

A method for rectifying thermograms in perspective captured at human height is proposed. It applies to the image pixel-by-pixel corrections that account for the surface emissivity, the reflected longwave infrared radiation flux, and the radiation emitted and attenuated by the atmosphere. The results are validated in two steps: first by comparison with contact temperature devices and then by comparison with finite element simulations. They give satisfactory results in both cases. The method is illustrated on a canyon-type street located in a dense urban area during a winter period of 24 h. Detailed observation of urban façade surface temperatures opens up new perspectives. Indeed, it allows conclusions to be drawn about the energy behavior of inhabitants by offering a non-intrusive alternative for identifying urban thermal bridges. Furthermore, the combined use of measurement and simulation facilitates the exploration of the thermal and optical properties of the scene. This work contributes significantly to the interpretation of urban metering at human height. It provides essential improvements in the evaluation of errors associated with urban surface temperatures retrieved from remote sensing observations. •Observations of urban surface temperature over 24 h at human height.•Rectification of perspective thermography by raytracing.•Results match very well with contact temperature measurements.•Spatialized information shows good agreement with FEM urban thermal simulations.•The method is a non-intrusive solution for identifying urban thermal bridges.