Does anybody know where much of this data comes from?
It says that many of these files are updated once or twice a year from "an outside source." Some have tens or hundreds of thousands of points, what outside source / company is doing all this work?
We've compiled a lot of data in the larger files from government agencies. There are good GIS resources at all levels -- Federal, state and local.
The "fun" part is stiching it together and formatting it to work with GPS.
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