n. The principle that each point of an advancing wave front is, in fact, the center of a new independent disturbance and thus the source of a new train of waves.
Huygen’s principle recognizes that the advancing wave, as a whole, may be regarded as the sum of all the secondary waves arising from points in the medium already traversed. Huygen’s principle is applied in spatial fire modeling by treating each point on a fire’s perimeter as the source of an independent elliptical fire. Information required at each point includes 1) orientation of the point at the fire front, 2) rate of spread and direction of maximum spread, and 3) elliptical dimensions of an elliptical fire determined from local fire environment conditions at that point. Within the fire behavior model FARSITE, Richard’s (1990, 1995) method is used to implement Huygen’s principle (Finney 2004).