A FIRE PERIMETER EXPANSION ALGORITHM-BASED ON HUYGENS WAVELET PROPAGATION

To model the spread of the perimeter of a wildfire, the perimeter can be regarded as a continuous curve, or more simply as a discrete number of points, which approximate the curve. Each point on the perimeter c an be regarded as a point source which expands as a small ellipse. The parameters of each ellipse depend on the local fuel type, slope and m eteorological conditions and the time step. According to Huygens' prin ciple, the envelope of these ellipses describes the new perimeter. Wit h discontinuous terrain and fuel, the perimeter may become complex, de veloping concavities and surrounding areas of low rate of spread. An a lgorithm which defines this envelope has been developed as part of the National Bushfire Model (a real-time computer application for persona l computers).