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I am working with U.S. National Landcover Dataset (NLCD) to classify habitat type at more than 150 sites across the northeast U.S. The dataset is very large (15GB) so I cannot upload it here, but it comes in .img format at 30m resolution. I have GPS coordinates in decimal degrees (WGS1984) for the center point of all the sites. I would like to be able to extract the proportion of landcover classes in a 1 square kilometer around the point. My questions are:

  1. How do I upload .img files into ArcGIS?
  2. How do I extract the information from around the GPS coordinates as proportions of the different habitat classes?
  3. How do I project my sites onto the NLCD map?
  4. Should I change the projection of my coordinates?
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I am also interested in doing this in r but I cant even get my sites to project on the same map either. Any advice would help. –  I Del Toro Apr 9 '13 at 1:30
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Does the .img have a projection assigned? Does it have coordinates? Do you have ERDAS Imagine or ENVI at hand? ArcGIS should be able to read .img files directly, as far as i can remember. Have you tried, and with what results? –  til_b Apr 9 '13 at 8:26

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I would try something like the following as a loose workflow:

  • a) buffer around the points (arcmap has a flat option to get 1km^2).
  • b) merge those into a single feature class to overlay on the whole map.
  • c) use the results from a) to clip tiles from the NLDS to find the data present.
  • d) compile the results from c).
  • e) compare results from d) to the whole map.

This assumes that you would be okay with a bit programming.

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