Fire shapes and the adequacy of fire-spread models

It has been suggested that shapes of burned areas resulting from fires spreading under uniform fuel and meteorological conditions may be described as ellipses, double ellipses, or ovoids. The adequacy of these shapes (together with simulation outputs) as bases for fire spread models was tested by finding the best fits of each shape to maps of experimental fires and comparing the results with fits given by a rectangle (an unlikely fire shape). Each of the models (ellipse, double ellipse, ovoid, simulation model, and even the rectangle) provided adequate approximations to the fire contours used in the tests. The parameter trends found implied that the fires examined tended to become more nearly elliptical in shape and to have higher eccentricity as they grew.