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Many digital map files are very large, ranging in size from several to several hundred megabytes. Large files include DOQs, DEMs, NEDs, LandSat, and SPOT. Browsers using phone-modem connections may take several hours to download a single map. The target audience for these files is experienced GIS users having high speed Web connectivity. A pilot project is in progress to convert some of our files to a smaller and easier to use format (.djvu) which will facilitate phone-modem access (see our Historic and Contemporary Maps of Nevada and Its Borders collection). If you are unable to download Big Files we can provide CD-ROM copies on a limited, fee-basis. We will direct large volume requests to the appropriate USGS or NASA sales office. Updated 16 November 2005 |
