■ Spectral imaging for remote sensing of terrestrial features and objects arose as
an alternative to high-spatial-resolution, large-aperture satellite imaging systems.
Early applications of spectral imaging were oriented toward ground-cover
classification, mineral exploration, and agricultural assessment, employing a
small number of carefully chosen spectral bands spread across the visible and
infrared regions of the electromagnetic spectrum. Improved versions of these
early multispectral imaging sensors continue in use today. A new class of sensor,
the hyperspectral imager, has also emerged, employing hundreds of contiguous
bands to detect and identify a variety of natural and man-made materials. This
overview article introduces the fundamental elements of spectral imaging and
discusses the historical evolution of both the sensors and the target detection
and classification applications.