FLAASH

FLAASH (Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes) is atmospheric correction software from Spectral Sciences, Inc. (SSI). Spectral imagery of the Earth's surface taken from aircraft or satellites is distorted by aerosols, water vapour and other atmospheric effects, and can be used to full advantage, for example for surface classification and material detection, only once those effects are removed and the data are reduced to surface reflectance.

FLAASH converts radiance imagery from visible, near-infrared and shortwave-infrared hyperspectral and multispectral sensors, viewed at nadir or off-nadir, into surface reflectance. It performs its radiation transport calculations with an embedded version of SSI's MODTRAN model and includes water vapour and aerosol retrieval, adjacency-effect correction and spectral polishing. Because the method is physics-based, it does not need known reflectance targets in the scene, which SSI says suits large-area work such as agriculture and land use. With hyperspectral input it can also output a column water vapour image and a cloud map.

SSI developed FLAASH with the US Air Force Research Laboratory, with support from NASA and other US government agencies, and the commercial ENVI version has been in widespread use in the hyperspectral community since its introduction in December 2001. It is sold in two forms: within the Atmospheric Correction Module for NV5's ENVI image processing software, where it can also be scripted as an ENVI task and, SSI says, used by non-expert analysts with minimal training, and as a stand-alone C++ module from SSI for embedding in batch processing systems. SSI reports that commercial profitability has been demonstrated in mineral prospecting and precision agriculture.