3D Modeling of satellite spectral images, radiation budget and energy budget of urban landscapes

16 DART EB is a model that is being developed for simulating 17 the 3D (3 dimensional) energy budget of urban and natural 18 scenes, possibly with topography and atmosphere. It simu19 lates all non radiative energy mechanisms (heat conduction, 20 turbulent momentum and heat fluxes, water reservoir evo21 lution, etc.). It uses DART model (Discrete Anisotropic 22 Radiative Transfer) for simulating radiative mechanisms: 23 3D radiative budget of 3D scenes and their remote sensing 24 images expressed in terms of reflectance or brightness tem25 perature values, for any atmosphere, wavelength, sun/view 26 direction, altitude and spatial resolution. It uses an innova27 tive multispectral approach (ray tracing, exact kernel, dis28 crete ordinate techniques) over the whole optical domain. 29 This paper presents two major and recent improvements of 30 DART for adapting it to urban canopies. (1) Simulation of 31 the geometry and optical characteristics of urban elements 32 (houses, etc.). (2) Modeling of thermal infrared emission by 33 vegetation and urban elements. The new DART> version 34 was used in the context of the CAPITOUL project. For that, 35 districts of the Toulouse urban data base (Autocad format) 36 were translated into DART scenes. This allowed us to 37 simulate visible, near infrared and thermal infrared satellite 38 images of Toulouse districts. Moreover, the 3D radiation 39 budget was used by DARTEB for simulating the time evo40 lution of a number of geophysical quantities of various sur41 face elements (roads, walls, roofs). Results were successfully 42 compared with ground measurements of the CAPITOUL 43 project.