• County data is provided in both .jpg and .img format.
  .JPG is a compressed image format, in which information is lost; little to no analysis can be performed on a .jpg image. It is mostly just for "looks." This is the recommended format for the general public.
  .IMG is a file format specific to the Imagine GIS and remote sensing software package. .IMG files are very large. This format is provided for scientists and resource managers with access to remote sensing and GIS software.
  
• Explanation of RGB and bands.
  The human eye is sensitive to red, green, and blue (RGB) wavelengths. Remote sensing instruments can detect energy from a much wider range of wavelengths. However, any band within the energy spectrum must be displayed as a visible wavelength when the data is represented as an image.
  The satellite sensor used to produce the county data, Landsat Thematic Mapper (TM), captures several different "bands" within the spectral range at a resolution of 30 meters. The bands used in the pictures of the county data are from 1 - 5. Band 1 (blue) = .45 - .515 micrometers. Band 2 (green) = .525 - .605 micrometers. Band 3 (red) = .630 - .690 micrometers. Band 4 (near infrared) = .750 - .900 micrometers. Band 5 (near infrared) = 1.55 - 1.75 micrometers. Band 6 (thermal) = 10.40 - 12.50 microns. Band 7 (mid-infrared) = 2.09 - 2.35 microns. The links to multispectral data provide the all 7 bands in Imagine (.IMG) format. Objects on Earth reflect differently in different bands, depending on which wavelength is used to remotely sense them. Multispectral images are avaliable for downlod as well.
  
• Software and methods.
  A type of remote sensing and GIS software, called Imagine, produced both the .JPG's and .IMG's. The shape of each county was used to extract the images you see from full Landsat TM scenes. Scenes are simply the total area captured by a single picture, organized by path and row. West Virginia lies within path 16 rows 32 - 34, path 17 rows 32 - 34, and path 18 rows 32 - 34.
  
• Explanation of images available in county shape.
  DEM (Digital Elevation Model) -- Illustrates relief in terrain. High elevations are displayed in light tones. Low elevations are displayed in dark tones.
  
  Painted relief -- representation of how topography might appear using artificial illumination and different colors for variation in elevation.
  
  Three color composites are provided:
  (1) simulated natural color (RGB = 3,2,1) -- This band combination is as the name states; it simulates the "natural colors" one might see with the naked eye.
  (2) false color (RGB = 4,3,2) -- The standard color representation in which vegetation generally appears red.
  (3) false color (RGB = 5,4,3) -- False color representation includes red displayed as blue, near infrared displayed as green, and mid infrared displayed as red. This band combination was chosen because it tends to distinguish different land cover material well.

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