Tree Crown Extraction using a Three State Markov Random Field

We present a new model for extracting tree crowns from aerial images, containing a near infrared channel. We addres s the problem as an image segmentation problem solved by a Markov Random Field (MRF) modeling embedded in a Bayesian framework. The prior model consists of a couple field defined by a three state MRF, associated to vegetation, background and center of trees, and a template field representing the tree shape. A template field allows to associate an ellipse to model the crown of each detected tree. The mod el is optimized by a simulated annealing scheme based on a Metropolis dynamics. We show some results on real images of manmade plantations and natural forests

Isotropic Properties of Some Multi-body Interaction Models: Two Quality Criteria for Markov Priors in Image Processing

Gibbs Fields are widely used in image processing for both segmentation and restoration. Defined on a discrete lattice representing the image they exhibit a non-isotropic behavior. Herein, we study and quantify this non-isotropy by computing the boundary tension as a function of the angle of a line separating the plane in two parts containing a different phase. From this study, we derive two quantitative criteria of the non isotropy of the model. We then compute the shape at zero temperature of a droplet of one phase within the other phase and study the non-isotropy of the shape for the different models. Finally, we show the artifacts due to this non-isotropic behavior for image segmentation and restoration

Large deviations for tandem queueing systems

The crude asymptotics of the large delay probability in a tandem queueing system is considered. The main result states that one of the two channels in the tandem system defines the crude asymptotics. The constant that determines the crude asymptotics is given. The results obtained are based on the large deviation principle for random processes with independent increments on an infinite interval recently established by the authors