Horizon GeoImaging

Advanced Remote Sensing and Digital Imaging

Horizon GeoImaging, LLC Spectral Expert Page

An expert system, the “Spectral Expert”® has been implemented for identification of materials based on extraction of key spectral features from visible/near infrared (VNIR) and shortwave infrared (SWIR) reflectance spectra and hyperspectral imagery (HSI). Spectral absorption features are automatically extracted from a spectral library and each is analyzed to determine diagnostic features and characteristics – the “rules”. An expert optionally analyzes spectral variability and separability to create refined rules for identification of specific materials. The rules can be used by a non-expert to identify materials by matching individual feature parameters or with a rule-controlled RMS approach. The result for a single spectrum is a score between 0.0 (no-match) and 1.0 (perfect-match) for each specific material in the spectral library, or for hyperspectral data, a classified image showing the predominate material on a per-pixel basis and a score image for each material. A feature-based-mixture-index (FBMI) score or image is also created, which alerts the analyst to possible problem spectra and mixing. This can be used to determine iterative expert system processing requirements for determination of secondary materials and assemblages and to point the analyst towards supplementary analyses using other non-feature-based methods.

The main outcome of our Spectral Expert research is approaches, algorithms, and methods implemented in a unified software prototype, the “Spectral Expert” developed within the framework of the ENVI software and the associated IDL programming language. The software is designed to allow non-experts to perform spectral feature analysis utilizing spectral libraries, variability statistics, and a rule-based expert system. It plugs seamlessly and automatically into ENVI/IDL and provides spectral viewing and analysis capabilities beyond base ENVI functionality, thus leading to an improved understanding of reflectance spectra and hyperspectral data. The software performs comparison of unknown spectra against the defined rules (the knowledge base) to permit identification of candidate materials based on scoring of matched rules. We plan to make the Spectral Expert software available to the public during 2008.

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®Spectral Expert is a registered Trademark of Horizon GeoImaging, LLC (Updated 02/14/2008 )