Application of rangefinder for small forest fire detection

Detection of fire smoke plume with a compact cheap rangefinder based on 905 nm laser diode (2 μJ pulse energy, slashed oh 2 cm telescope and 720 m solid-target range) is demonstrated. Reliable detection of small experimental fires (20×25 m2 fire plot, burning rate of ~3 kg/s) is achieved for the range of about 255 m. A theoretical model of the mixing of burning products with air in the wind, based on three-dimensional system of Navier-Stokes equation and commercial software PHOENICS, is developed. The model predicts 220 m range of smoke detection by the rangefinder, indicating good agreement between the theoretical and experimental data. On the basis of this theoretical model an estimation of the smoke detection efficiency for a longer range (20 km for solid targets) instrument, based on a 1540 nm laser with a pulse energy of 8 mJ and a 4 cm telescope, is made. The obtained smoke-detection range estimation, 6 km, indicate that more powerful rangefinders can be used not only in shot-range applications, such as fire detection in premises, tunnels and storage yards, but in more demanding areas, such as wildland fire surveillance, as well.

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