**4. Conclusions and future perspectives**

An innovative methodology using a 3D RT modeling and satellite reflectance data to derive urban surface albedo images has been designed and implemented. The method was tested using an atmospherically corrected Landsat‐8 multispectral image of the city of Basel. Although the preliminary results are encouraging, the newly presented methods have to be still properly validated. Different validation approaches are foreseen for testing their robust‐ ness:


A comprehensive comparison of the direct and iterative method technical performances is also required. It is especially important for future transformation of the methodology into a standardized operational approach.

Another important development lies in finalization of the thermal infrared spectral domain calibration. Combination of both calibrations in the visible and thermal part of the electro‐ magnetic spectrum would lead to a complete 3D radiative budget produced by DART at the same time as the other RT products.

To summarize, an original methodology for deriving urban surface albedo images from remote sensing data without a need of in situ measurements was implemented, although ground measurements could improve the final results. Both calibrations are computationally opera‐ tional, but the results forthe iterative method are considered as preliminary, due to the limited implementation of only a single iteration. Iterative method is expected to be more accurate than for the simpler direct one. Nevertheless, the direct calibration might prove to be easier to use and more robust in case of inaccurate urban datasets, which depends on spatial resolu‐ tion and geometric co‐registration of DART and satellite imagery. Finally, both methods rely on the fact that DART is a reliable RT model simulating both satellite images and the radia‐ tive budget of cities with an acceptable accuracy. In a perspective of increasing remote sensing data availability, arising from new satellite systems such as Sentinel‐2, these approaches are expected to play an important role in future surveys of cities and their dynamic climate.
