This is a correction to a posting I made in the now-obsolete forum:
http://developer.coronalabs.com/forum/2013/01/27/problem-extenting-gps-sample-program
I discovered that the Corona SDK GPS sample program works OK as is, and that it the modification I described was an error. In that modification I restarted the GPS periodically with a timer. That did make the GPS appear to work OK, but it was using just the WiFi to get its position. Restarting the GPS periodically the way I described did not give the GPS sufficient time to get a satellite fix. The Corona SDK uses the WiFi fix to get a preliminary fix the assist the GPS in getting a satellite fix, which takes some time, perhaps almost a minute.
The GPS sample program works properly just as it is. I used that technique in a program of my own, and it works OK there too.
Ted