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CASI Multispectral Imagery

Published by Environment Agency

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Dataset of Compact Airborne Spectrographic Imager (CASI) multispectral imagery collected for England, published by the Environment Agency. CASI is a pushbroom sensor capturing visible and near-infrared light across up to 288 discrete bands, typically around 20, enabling targeted analysis of ground characteristics such as vegetation type, biomass, chlorophyll absorption or algae fluorescence. Data were acquired on a project basis rather than as complete national coverage, and are supplied as time-stamped GeoTIFF tiles of 5km by 5km covering discrete wavelength layers, without image balancing or atmospheric correction. Users should consult metadata catalogues for survey dates, spatial resolution and band counts, and apply GIS or specialist image-processing software for analysis.”}}Compact Airborne Spectrographic Imager is a multispectral pushbroom system that acquires data in visible and near infrared (VNIR) light. Unlike camera systems that generally acquire data in three (red, green, blue) or four (red, green, blue and near infra-red) bands, the CASI splits light into several discrete bands, up to 288, although approximately 20 are more normally captured. It is capable of collecting data in discrete areas of the electromagnetic spectrum and can target key wavelengths that allow information about ground characteristics and ground cover type to be inferred. For example, the CASI can target the precise wavelengths of chlorophyll absorption or the algae fluorescence peak. CASI data have been acquired on a project basis, so there are not extensive datasets. These datasets have generally been acquired where the limited spectral information in aerial photography would not be sufficient to map a specific variable, such as a specific vegetation type or biomass. CASI data are supplied in time-stamped GeoTIFF format as 5km by 5km tiles of the image mosaic. The tiles consist of a series of image layers representing discrete wavelengths. There has been no image balancing or atmospheric correction applied to the flight lines. Hence, lighting differences maybe apparent in the image mosaics. There are ways of mitigating against these effects, for instance applying band ratio techniques. CASI data should be used within either GIS or specialist image processing software for results. Please refer to the metadata index catalgoues for the survey date captured, spatial resolution of the imagery and number of wave bands present in the data. Attribution statement: © Environment Agency copyright and/or database right 2016. All rights reserved.