Overview of This Tutorial - Department of Geosciences

Tutorial: Hyperspectral Signatures and Spectral Resolution
19. Compare the apparent reflectance spectra to the library spectra, by dragging and dropping spectra
from the ENVI Plot Window into the Spectral Profile.
20. See
Draw Conclusions on page 19, and answer some of the questions pertaining to Landsat TM data.
21. When you are finished, close the display group, ENVI Plot Window, and Spectral Profile. Keep the
Spectral Library Plots window open for the remaining exercises.
View GEOSCAN Image and Spectra
The GEOSCAN MkII sensor, flown on a light aircraft during the late 1980s, was a commercial aircraft system
that acquired up to 24 spectral channels selected from 46 available bands. GEOSCAN covered a spectral range
from 0.45 to 12.0 µm using grating dispersive optics and three sets of linear array detectors (Lyon and Honey,
1989).
GEOSCAN's high spatial resolution makes it suitable for detailed geologic mapping (Hook et al., 1991). A
typical data acquisition for geology resulted in 10 bands in the visible/near infrared (VNIR, 0.52 - 0.96 µm), 8
bands in the shortwave infrared (SWIR, 2.04 - 2.35 µm), and thermal infrared (TIR, 8.64 - 11.28 µm) regions
(Lyon and Honey, 1990). The relatively low number of spectral bands and low spectral resolution limit
mineralogic mapping to a few groups of minerals in the absence of ground information. However, the strategic
placement of the SWIR bands provides more mineralogic information than expected under such limited
spectral resolution.
The following plot shows ROI mean spectra for kaolinite, alunite, and buddingtonite. The spectra for these
minerals appear quite different in the GEOSCAN data, even with the relatively widely spaced spectral bands.
View GEOSCAN Mean Kaolinite and Alunite Image Spectra
1. From the ENVI main menu bar, select Window → Start New Plot Window. A blank ENVI Plot
Window appears.
2. From the ENVI Plot Window menu bar, select File → Input Data → ASCII. A file selection dialog
appears.
9
ENVI Tutorial: Hyperspectral Signatures and Spectral Resolution