Characterization of Urban Surface Materials using Airborne Imaging FTIR Spectroscopy: First Results from a Campaign in Dessau, Germany

Imaging Fourier-Transform Infrared (FTIR) spectroscopy in the long-wave infrared (LWIR) domain (7–14 µm) offers unique capabilities for the identification and mapping of surface materials based on their distinct spectral emissivity signatures. While laboratory applications are well-established, airborne deployment for complex urban environments remains a developing field. This study presents initial results from a recent test campaign conducted on the 20^th of May 2025 in Dessau, Germany by utilizing the Telops Hyper-Cam Airborne Mini. The objective of this research was to evaluate the sensor's capability to detect and discriminate common urban surface materials such as concrete, asphalt, roofing tiles, and potentially polymers and metals under real-world flight conditions. The hyperspectral data cubes were acquired over an industrial urban area at an altitude of around 800 meters above ground resulting in a resolution of 60 cm per pixel with a spectral resolution of 6.5 wavenumbers. The airborne measurements were validated through comparison with a laboratory-based spectral reference library acquired under controlled conditions. The comparison with laboratory spectra provides critical insights into the reliability of airborne FTIR data. In particular, we utilized a spectral library developed by King’s College London as a reference standard, consisting of representative material samples collected from the London area. We performed a comparative analysis between the atmospherically corrected airborne emissivity spectra (processed by FLAASH-IR) and the laboratory emissivity reference signatures. The results demonstrate a strong correlation between the airborne data and the laboratory measurements. Specifically, the system showed high proficiency in distinguishing between silicate-based materials and metal due to their characteristic absorption and emissivity features in the LWIR region. However, challenges remain in classifying asphalt, solar panels, and roofing materials due to surface conditions and low spectral contrast as well as the problem of spectral mixing. This study highlights the potential of the Telops Hyper-Cam Airborne Mini for hyperspectral urban material mapping and addresses challenges that need to be solved in the future. Our findings contribute to a better understanding of urban surface heterogeneity and support the planning of future airborne campaigns for urban planning and environmental monitoring applications.

This research is funded by the German Research Foundation (DFG, grant number: 514067990).