Characterization and delineation of plumes, clouds and fires in hyperspectral images

Techniques for scene characterization can utilize individual or combinations of visible and IR spectral bands to identify specific features in an image. This paper deals primarily with the problem of characterization of a partially smoke- or cloud-filled atmosphere. Proper analysis of the scene allows further sensing of underlying surface features such as actively burning and burn scarred regions. Both a physics-based and a semi-automated feature extraction approach are used for identifying and characterizing features in a set of AVIRIS scenes dominated by areas of smoke plumes, clouds and burning grassland as well as burnt vegetation. A combination of the two approaches is used to both discriminate and classify various features in a smoke/cloud filled scene. An AVIRIS scene chosen for initial testing of the two algorithms was collected on 20 August 1992 in the foothills east of Linden, California. A typical AVIRIS scene covers a 10 km×10 km area at 20 m pixel resolution and 224 contiguous spectral bands of data over the range 400 to 2500 nm. The scene consists of a grass fire producing a thick plume of smoke extending toward the east. A cloud produced by the thermal properties of the fire overlies the smoke plume. Northwest of the main fire, two smoldering fires produce a thin veil of smoke that covers much of the upper half of the scene. The southwest portion of the scene is cloud and smoke free. This scene provides a variety of atmospheric and surface features from which to orient and characterize. A plot of the apparent reflectance of various identified features was made. The cloud is significantly brighter than the smoke over the entire spectral region