Calibration

Dates

Publication Date: 2018-12-11
Start Date: 2014
End Date: 2016

Citation

Hoefen, T.M, Johnson, M.R., Kokaly, R.F., Graham, G.E., Kelley, K.D., and Hubbard, B.E., 2018, Corescan© Hyperspectral Core Imager, Mark III system data collected for the characterization of mineral resources near Nabesna, Alaska, 2014-2016: U.S. Geological Survey data release, https://doi.org/10.5066/F7057DWM.

Summary

Measurements of reference materials were made on the Corescan© HCI-III to evaluate the supplied channel wavelength positions and bandpass values. Wavelength position and bandpass of channels in a spectrometer, referred to as full-width half max (FWHM) in the contractor's documentation (Corescan_Product_MetaData_v3.pdf), are two fundamental spectral characteristics that need to be known in order to spectrally identify minerals by comparison to a spectral library, like the Material Identification and Characterization Algorithm (MICA) analysis used to generate the mineral predominance maps. Spectrometers with finer bandpass can reveal greater spectral detail that can be related to a material’s chemical composition or physical structure: [...]

Summary

Measurements of reference materials were made on the Corescan© HCI-III to evaluate the supplied channel wavelength positions and bandpass values. Wavelength position and bandpass of channels in a spectrometer, referred to as full-width half max (FWHM) in the contractor's documentation (Corescan_Product_MetaData_v3.pdf), are two fundamental spectral characteristics that need to be known in order to spectrally identify minerals by comparison to a spectral library, like the Material Identification and Characterization Algorithm (MICA) analysis used to generate the mineral predominance maps. Spectrometers with finer bandpass can reveal greater spectral detail that can be related to a material’s chemical composition or physical structure: for example, kaolinite crystallinity. Imprecise knowledge of wavelength positions of channels could interfere with interpreting a material’s composition from its spectral feature positions: for example, interpreting Al composition in white mica from wavelength shifts in the absorption feature centered near 2,200 nm. Because, push broom imaging spectrometers, like the Corescan HCI-III, can sometimes have variable spectral characteristics across the field of view, the channel wavelength positions across the field of view were also evaluated.

The imaging spectrometer raw data was collected with an average bandpass of approximately 6 nm across the Short Wave Infrared (SWIR) but smoothing functions applied by Corescan during the conversion of raw data to reflectance result in a relative bandpass of approximately 13 nm in the data delivered to the U.S. Geological Survey (USGS). Wavelength evaluations of the imaging spectrometer data revealed that the supplied wavelength values should be shifted and, thus, adjustments were made to the wavelength positions (Kokaly and others, 2017). The wavelength and bandpass evaluation results are provided in this section of the data release and were used to adjust the Corescan reflectance data.

References Cited

Kokaly, R.F., 2011, PRISM: Processing routines in IDL for spectroscopic measurements (installation manual and user's guide, version 1.0): U.S. Geological Survey Open-File Report 2011–1155, 432 p., available at https://pubs.usgs.gov/of/2011/1155/.

Kokaly, R.F., Hoefen, T.M, Graham, G.E., Kelley, K.D., Johnson, M.R., Hubbard, B.E., Buchhorn, M., and Prakash, A., 2017, Hyperspectral outcrop imaging of the Orange Hill porphyry copper deposit, Alaska, USA, paper 84, Exploration 17 Integrated Earth Sciences Conference, Toronto, Canada, October 21-25, 2017, available at http://www.exploration17.com/Exploration17/media/documents/Exploration-17-Conference-Proceedings.zip.

Contacts

Point of Contact :: Todd M Hoefen
Originator :: Todd M Hoefen, Michaela R Johnson, Raymond F Kokaly, Garth E Graham, Karen D. Kelley, Bernard E Hubbard
Metadata Contact :: Michaela R Johnson
Publisher :: U.S. Geological Survey
Distributor :: U.S. Geological Survey - ScienceBase
SDC Data Owner :: Geology, Geophysics, and Geochemistry Science Center
USGS Mission Area :: Energy and Minerals

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Corescan©HyperspectralData_NabesnaAK2014to2016_20181114_CALIBRATION.xml Original FGDC Metadata	View	23.02 KB	application/fgdc+xml
corescan_channel_adjustedwavelength_evaluatedbandpass.csv		10.49 KB	text/csv
corescan_channel_suppliedwavelength_adjustedwavelength.csv		9.3 KB	text/csv
CorescanHCI-III_bandpass_native_and_smoothed.jpg		1.24 MB	image/jpeg
CorescanHCI-III_wavelength_adjustments.jpg		1.53 MB	image/jpeg
CorescanHCI-III_xtrack_native.jpg		2.37 MB	image/jpeg
CorescanHCI-III_xtrack_smoothed.jpg		2.48 MB	image/jpeg

Purpose

HCI-III data were collected as one component of a USGS mineral resource project with the goals of enhancing geologic mapping and developing methods to identify and characterize mineral deposits elsewhere in Alaska through the use of imaging spectroscopy. HCI-III data were collected on hand samples to validate airborne HyMap imaging spectrometer results.

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