Hyperspectral sensing has become an industrial tool, particularly in geological exploration programs. Extremely large volumes of image data are collected with airborne spectrographic imagers. The image data must be processed and analyzed efficiently. To support this, various metadata about the mission and the sensor must be attached to the image data in a consistent manner. This capability is provided by the image metadata support new to Version 9.0 of Catalyst Professional, described in further detail at Image metadata support.
The processing software should minimize the need to generate versions of images that represent intermediate processing steps since the original data alone may demand a large data storage capacity. The new image metadata support helps by accommodating the storage of gain and offset values for a sequence of radiometric transformations. So, for example, instead of requiring the creation and storage of an "at-sensor radiance" image derived from the original sensor output image, and then a "scene reflectance" image derived from the at-sensor radiance image, the user can store the parameters of the radiometric transformation from sensor response to at-sensor radiance, and at-sensor radiance to reflectance in the image metadata. The programs in the Hyperspectral Analysis Package allow the user to specify the application of all or part of the radiometric transformation sequence on image input.
Many hyperspectral processing and analysis operations require the use of reflectance spectra measured in a laboratory or in the field, on the ground. New support for reflectance spectra input/output has been included in the GDB technology for CATALYST Pro Version 9.0. Reflectance spectra can be read into the Advanced Hyperspectral Package programs directly from USGS "Specpr" format binary files, text files, or Excel spreadhseet (.xls) files. Spectra that have been input or derived from image data can be written to Specpr, text, or Excel spreadsheet files. The GDB spectra I/O support is discussed in further detail at Spectra input/output.
Reflectance spectra from a laboratory or field source will not generally have a waveband sampling that matches the band sampling of the imaging spectrometer whose data are to be analyzed. Hyperspectral Analysis Package programs that read spectra and use them to process image data are able to resample the input spectra "on the fly" to match the waveband sampling of the image data. The image metadata hold the band response profiles that are required to do this. Spectra can also be resampled and the results saved to a file using SPCONVP (see Spectra handling).
The Advanced Hypersepectral Package programs can process arbitrarily large images on common desktop personal computers with modest RAM resources (large RAM resources are taken advantage of, if available). Large images need not be divided into multiple smaller images before processing. This simplifies data management.
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