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=See Also=
* [[OpenStreetMap]]
=Links=
* [[w:Geographic information system|Wikipedia's Geographic information system article]]
* [http://www.oreillynet.com/wireless/2000/12/29/two_gps.html The difficulties of a poor man's differential GPS]
* [http://code.google.com/p/googletransitdatafeed/wiki/PublicFeeds Public Google Transit Feeds]
