In many applications we can deploy large number of sensors spanning wide geographical areas, to monitor environmental phenomena. The analysis of the data collected by such sensor network can help us to understand the field dynamics, and optimize the deployment of other solutions. We define a group of sensors having similar underlying distribution over a period of time as a homogeneous region. In this paper we propose distributed algorithms to detect such regions, approximate their boundary with a piece-wise linear curve and track the boundary in real-time. Experimental results show the accuracy and efficiency of our detection and tracking algorithms.