Atmospheric attenuation and scattering determined from multiheight multispectrat scanner imagery

Multispectral imagery was obtained at six altitudes from 500 to 3000 m over a single site on a hazy day. At each altitude, digital values— proportional to radiance—were averaged over selected areas on the ground. The effect of scattering was eliminated by taking differences between areas and the attenuation coefficient determined from the change with altitude. Values ranged from 0.1 km−1 in the near-infrared to 0.3km−1 in the blue wavebands. The scattering was determined by applying these coefficients to the original data. In all bands the scattering profile varied considerably with height with a peak in the 1000-1500m layer. This peak corresponded to a layer of high humidity found in the radiosonde data and suggests the presence of hygroscopic aerosol. The airborne data were extrapolated to the ground and were calibrated by reference to a reflectance measurement at the surface. It is proposed that such multiheight techniques could be used as a means of correcting for atmospheric effects in applications of remote sensing where radiometric fidelity is important, Additional informationNotes on contributorsM. D. STEVEN Now in Department of Geography J. B. MONCRIEFF Department of Trade and Industry Warren Spring Laboratory, Stevenage, Herts., England.