Spectral reflectance data are central to the mapping of urban surfaces and materials from satellite and aerial imagery. The number of available samples is very small for the variability of materials within each category (e.g., asphalt). Many factors impact surface reflectance, because of material composition linked to national/local regulations related to weather/climate conditions, local availability of raw materials and socio-economic factors. To help address this data-gap, the rurbisphere spectral library is being developed, using RS-3500 spectroradiometer and HySpex Mjolnir VS-620 camera. Both sensors captures spectral radiation from 410nm to 2500nm with less than 5nm spectral resolution. This will use observations taken in several European cities, such as Paris, Berlin, Bristol, Heraklion and Limassol.

The urbisphere hyperspectral measurements are organized to clusters (groups of HS measurements with similar reflectance spectrum). Each measurement is delivered with its own image, measurement ID, spectral reflectance, unique material name/color/structure/status/usage/location, spectral incoming radiation, spectral outgoing radiation and metadata for the quality and the conditions during the measurements. The spectra are also adjusted to several multispectral and hyperspectral Satellite sensors (PRISMA, EnMap, Sentinel-2, Landsat-8, Planet SuperDove, WorldView-3). The adjusted spectra can be used directly for Machine Learning training for the respective L2A satellite images. A small sample of the urbisphere Library v1.0 is available below. The full version (v1.0) of the library, which includes 2,400 spectra organized in 120 clusters, will be avaliable after the relevant publication.

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