I got a GPS module from some outfit in China off ebay for something like four dollars, still haven't unwrapped it from stat bag.. No reason to think it's anything other than fine. I got a great deal, but it's reasonably easy to find them for around ten bucks or so I would imagine (thinking dealextreme or whatever).
I was reading and waiting for Crossroads to chime in.. So there's obviously a reason.. So what is it? I am talking about VORTAC, a radio beacon network that back in the stone age was used via signal triangulation off the frequency/tower chart to give pretty dang accurate positioning. I am supposing it's a resolution issue to use actual VORTAC, but (I really don't know) would low power radio triangulation work within the range of reasonable open air lower power beacons? GPS for large scale with finer granularity coming from triangulating off of local ground beacons of known position...
Per request, here's a thread...
Just a discussion of navigation methods and hardware, and the shortcomings of GPS.