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A multispectral image is one that captures image data at specific frequencies across the electromagnetic spectrum. The wavelengths may be separated by filters or by the use of instruments that are sensitive to particular wavelengths, including light from frequencies beyond the visible light range, such as infrared. Spectral imaging can allow extraction of additional information the human eye fails to capture with its receptors for red, green and blue. It was originally developed for space-based imaging. Multispectral images are the main type of images acquired by remote sensing (RS) radiometers. Dividing the spectrum into many bands, multispectral is the opposite of panchromatic, which records only the total intensity of radiation falling on each pixel. Usually, Earth observation satellite This technology has also assisted in the interpretation of ancient papyri, such as those found at Herculaneum, by imaging the fragments in the infrared range (1000 nm). Often, the text on the documents appears to the naked eye as black ink on black paper. At 1000 nm, the difference in how paper and ink reflect infrared light makes the text clearly readable. It has also been used to image the Archimedes palimpsest by imaging the parchment leaves in bandwidths from 365-870 nm, and then using advanced digital image processing techniques to reveal the undertext with Archimedes' work.〔(【引用サイトリンク】url=http://archimedespalimpsest.org/about/imaging/ )〕 The availability of wavelengths for remote sensing and imaging is limited by the infrared window and the optical window. ==Spectral bands== The wavelengths are approximate; exact values depend on the particular satellite's instruments: * Blue, 450-515..520 nm, is used for atmosphere and deep water imaging, and can reach depths up to in clear water. * Green, 515..520-590..600 nm, is used for imaging vegetation and deep water structures, up to in clear water. * Red, 600..630-680..690 nm, is used for imaging man-made objects, in water up to deep, soil, and vegetation. * Near infrared, 750-900 nm, is used primarily for imaging vegetation. * Mid-infrared, 1550-1750 nm, is used for imaging vegetation, soil moisture content, and some forest fires. * Mid-infrared, 2080-2350 nm, is used for imaging soil, moisture, geological features, silicates, clays, and fires. * Thermal infrared, 10400-12500 nm, uses emitted instead of reflected radiation to image geological structures, thermal differences in water currents, and fires, and for night studies. * Radar and related technologies are useful for mapping terrain and for detecting various objects. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Multispectral image」の詳細全文を読む スポンサード リンク
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