Estimation of Horizontal Diffusion from Oblique Aerial Photographs of Smoke Clouds

Richard M. Eckman Atmospheric Turbulence and Diffusion Division, NOAA/ARL Oak Ridge, Tennessee

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Torben Mikkelsen Riso National Laboratory, Roskilde, Denmark

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Abstract

A photogrammetric method is described for obtaining estimates of the horizontal diffusion parameter σy from oblique aerial photographs of smoke clouds. The method requires three reference markers on the ground to determine the geometry in each oblique photograph. Besides the distances between these markers, the only other independent information required for the method is the focal length of the camera lens and the enlargement factor of the photographs. The method is particularly useful for estimating σy at small sampling times, including relative diffusion. Additionally, it provides high spatial resolution in the downwind and crosswind directions and places no restrictions on the wind directions for which diffusion data can be collected.

Abstract

A photogrammetric method is described for obtaining estimates of the horizontal diffusion parameter σy from oblique aerial photographs of smoke clouds. The method requires three reference markers on the ground to determine the geometry in each oblique photograph. Besides the distances between these markers, the only other independent information required for the method is the focal length of the camera lens and the enlargement factor of the photographs. The method is particularly useful for estimating σy at small sampling times, including relative diffusion. Additionally, it provides high spatial resolution in the downwind and crosswind directions and places no restrictions on the wind directions for which diffusion data can be collected.

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