PhD defense - Guillaume Perrin

Defense : Monday, October 2nd 2006, 15h30, Ecole Centrale de Paris.

Title: Tree crown extraction using Marked Point Processes

Abstract: This thesis addresses the problem of tree crown extraction from Colour InfraRed (CIR) aerial images of forests. Our models are based on object processes, otherwise known as marked point processes. These mathematical objects are random variables whose realizations are configurations of geometrical shapes. This approach yields an energy minimization problem, where the energy is composed of a regularization term (prior density), which introduces some constraints on the objects and their interactions, and a data term, which links the objects to the features to be extracted. Once the reference object has been chosen, we sample the process and extract the best configuration of objects with respect to the energy, using a Reversible Jump Markov Chain Monte Carlo (RJMCMC) algorithm embedded in a Simulated Annealing scheme.

We propose different models for tree crown extraction depending on the density of the stand. In dense areas, we use an ellipse process, while in sparse vegetation an ellipsoïd process is used. As a result we obtain the number of stems, their position, the diameters of the crowns and the heights of the trees for sparse areas. The resulting algorithms are tested on high resolution CIR aerial images provided by the French National Forest Inventory (IFN).

Keywords: Marked point processes, RJMCMC, simulated annealing, automatic object extraction, forests, tree crowns, Colour InfraRed aerial images.

Manuscript : available online (in french).

Slides of the defense : available online (in french).

Movies : available online.