Map Information For All 48 States
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Digital Ortho Quarter Quads (Imagery)
This image data is produced by a consortium of federal and state agencies with the lead being the United States Geological Survey (USGS). It can exist as color or black and white photography. The images are refreshed across the country on a 5-7 year cycle so how current the images are varies.
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Digital Raster Graphics (Topo Maps)
These are also produced by the USGS. DRG's are digital representations of hard copy USGS Standard Series Topo maps. DRG's are commonly created by scanning the original hard copy map and then georeferencing the image so that it has positional coordinates and can be used in mapping applications. DRG's are refreshed on an annual basis.
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Google Base Layers
Google publishes color satellite imagery, terrain surfaces, and road/city networks. This information is compiled from commercial mapping companies.
