Biophysical parameter retrieval from forest and crop canopies in the optical and microwave domains using 3D models of canopy structure

3D structural models of a (dynamic) wheat canopy and a Scots pine canopy are used to drive models of canopy scattering behaviour in the optical and microwave domains. These models have been shown to be capable of simulating canopy reflectance and backscatter using scattering models in the optical and microwave domains. By varying the structural and radiometric parameters governing the simulated canopy response, look-up tables (LUTs) of reflectance (optical) and backscatter (microwave) are constructed. These LUTs are used to ´invert´ the scattering models against reflectance and backscatter observations made from airborne reflectance and SAR backscatter data. The practicability of this approach is demonstrated. It is shown that combined optical and microwave retrievals are possible without the need for simplified mathematical models of scattering behaviour and time-consuming numerical inversion techniques. Once LUTs have been generated, inversion against observations is very rapid and flexible.