Modeling tree architecture and forest dynamics. A research project in the dense moist evergreen forests of the Western Ghats (South India)

This working paper presents a research programme which aims at modelling the dynamics of the dense moist evergreen forests of the Western Ghats (India) from analysing, modelling and simulating tree architecture. The paper first reviews various approaches to modelling the dynamics of heterogeneous forests, either temperate or tropical: demographic matrix models, distance-dependent tree growth models, gap models, cellular automata and multiagent systems. The advantages and drawbacks of the architectural approach are then discussed. The proposed study site is then briefly presented and a programme is outlined: selection of some species which are both frequent and representative of the different forest strata, sampling strategy and measurements, methods used for modelling and computer simulation. The preliminary results obtained since the project was started in early 1995 are then briefly reviewed; a more detailed account will soon be published in another paper of this series

Cramer-Rao lower bound for the estimation of the degree of polarization in active coherent imagery at low photon level

International audienceThe degree of polarization (DOP) is an important tool in many optical measurement and imaging applications. We address the problem of its estimation in images that are perturbed with both speckle and photon noises, by determining the Cramer-Rao Lower Bound (CRLB) when the illuminated materials are purely depolarizing. We demonstrate that the CRLB is simply the sum of the CRLBs due to speckle noise and to Poisson noise. We use this result to analyze the influence of different optical parameters on DOP estimation