Empirical line correction

The EMPLINE program is used to compute parameters of band-specific radiometric transformations to transform multiband image values to estimates of scene reflectance. This program uses the Empirical Line Correction technique. This technique is empirical in the sense that it does not involve an analytical model of the image formation process. Rather, it relies entirely on a ground- or laboratory-measured reflectance spectrum for each of one or more surface types that can be localized in the image. Ideally, the spectra are measured on the ground during the sensor overflight, and the measuremnt locations are carefully selected such that they may be reliably found in the image and are homogenous over a broad eneough spatial extent to be represented by some pure pixels in the image.

This technique cannot take into account the effect of variations in atmospheric conditions over the full extent of the image. A single set of transformation parameters for each band is computed for the full image extent.