voice navigation using GPS

hi
i doing voice GPS based voice navigation for blind people, (concept is we create some location in maps, when the person crossed that location the voice will redout that location names) me purchased local GPS , the GPS give the latitude and longitude values, when i move the GPS the values are same in different location also, how to interface with maps or any customized maps available to do this projects,please give me a idea to do next level

thanks in advance