Tracking a rangeland fire with infrasound arrays

We present the first infrasound analyses of a rangeland fire and demonstrate infrasound’s potential in monitoring wildland fires. We recorded a prescribed fire in sagebrush steppe in cool, moist conditions, using eight infrasound arrays of diverse size (3-44 sensors, 10-200 m width) and distance (0-20 km), including arrays inside the burn area. Infrasound arrays within 2 km of fires detected coherent infrasound between 1-10 Hz, both during active ignitions and also while existing fires continued burning during breaks in ignitions. During periods of active ignitions, the direction of arrival estimated by a 44-sensor array closely tracked the actual locations where the helicopter was igniting vegetation. Despite being farther from the fire than four smaller arrays, the 44-sensor array performed best at identifying coherent infrasound and yielding consistent directions of arrival.