Observations on powder snow avalanches using videogrammetry

A large powder snow avalanche was artificially triggered at the Swiss Vallée de la Sionne test site on February 7th, 2003. Two synchronised digital video cameras were used to track manually identified features on the surface of the powder cloud. By identifying the same features on different cameras, their three-dimensional location was determined using stereoscopic projection. The surface of the avalanche was inferred from these measurements and used to calculate such quantities as flow height, flow volume and flow velocity.