Adjusting the tasselled-cap brightness and greenness factors for atmospheric path radiance and absorption on a pixel by pixel basis

A radiative transfer model was used to convert ground-measured reflectances into the radiance at the top of the atmosphere, for several levels of atmospheric path radiance. The radiance in MSS 7 (0.8-1.1 μm) was multiplied by the transmission fraction for atmospheres having different levels of precipitable water. The radiance values were converted to simulated Landsat digital counts for four path radiance levels and four levels of precipitable water. These values were used to calculate the Kauth-Thomas brightness, greenness, yellowness and nonesuch factors. Brightness was affected by surface conditions and path radiance. Greenness was affected by surface conditions, path radiance and precipitable water. Yellowness was affected by path radiance and nonesuch by precipitable water, and both factors changed only slightly with surface conditions. Yellowness and nonesuch were used to adjust brightness and greenness to produce factors that were affected only by surface conditions such as soils and vegetation, and not by path radiance and precipitable water.