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ENVI

SPEAR Pan Sharpening

SPEAR Pan Sharpening

Pan Sharpening is an image fusion method in which high-resolution panchromatic data is fused with lower resolution multispectral data to create a colorized high-resolution dataset. The resulting product should only serve as an aid to literal analysis and not for further spectral analysis.

The following shows a Pan-sharpened Product, High-Resolution Panchromatic Image Fused with Lower Resolution Multispectral Image (IKONOS Imagery Courtesy of GeoEye, Copyright 2007)

  1. From the Toolbox, select SPEAR > SPEAR Pan Sharpening. The SPEAR Pan Sharpening Wizard displays the File Selection panel.
  2. Click Select High Res File, select a panchromatic image, select the input band to use, then click OK.
  3. Click Select Low Res File, select a multispectral image, select the input band to use, then click OK. Simultaneous image collections are not required but will produce better results.
  4. To optionally process only a portion of the scene, select the High Res or Low Res image as the subset source, then click Select Subset. A small Select Spatial Subset dialog appears.
  5. Click Spatial Subset. The standard Select Spatial Subset dialog appears. When finished, click OK to return to the File Selection panel.
  6. By default, output files are saved to the same directory and use the same rootname as the input file, minus any extension. Output files are appended with a unique suffix. To change the directory and/or root filename, click Select Output Root Name.
  7. Click Next. The Method Selection panel appears with coregistration parameters.
  8. Set the coregistration parameters. Even if the images were acquired simultaneously, the georeferencing accuracy is seldom good enough to allow a straight fusion. Check the accuracy of the coregistration and fix tie points if needed.
  9. Use Auto-Flicker to examine your results.
  10. If you are coregistering for the Pan Sharpening tool, set the sharpening method to use:
  11. When coregistration is complete, click Next. The Processing Complete panel appears.
  12. The Spectral Quality Indices that appear on the Processing Complete panel are a way to gauge the degradation of the spectral properties of the multispectral bands due to the pan-sharpening process. For instance, Gram-Schmidt results in higher spectral quality indices than the Brovey Transform. The algorithm measures the correlation coefficient, brightness, and contrast between the input and output bands. Perfect spectral correspondence would result in a value of 1. These indices are for informational purposes.
  13. Optionally, Export Image to NITF.
  14. Optionally, click Export Image to ArcGIS Geodatabase. The Select Output Geodatabase dialog appears.
  15. When you are finished examining results, click Finish in the Processing Complete panel to exit the Wizard.

    The following shows Pan Sharpening Results using Different Methods (IKONOS Imagery Courtesy of GeoEye, Copyright 2007)



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