Radio Triangulation (GPS minus space) Answered
Okay, my idea is that in the event of the zombie apocalypse (or many others) I think it would be very handy to have a GPS-esque service. I've read that the satellites we use for GPS are decaying and will not be around for much longer than 20 or 30 years without repair or replacement. So, in the event that the zombies come and I manage to survive and, more importantly, thrive, I would like to be able to set something along these lines up.
Assuming I have access to renewable power sources and the correct materials, how would I build something like this? My initial thought is to use radio towers for triangulation. I go to three existing radio towers, set them up with a power source, and set them to frequencies A, B and C respectively. Then i have a (preferably mobile) device that monitors the signal strength of those towers. Another option that springs to mind is that i might have multiple antennae that i can connect to a few feet of wire each and place around my device for added accuracy. If my idea is sound, I then will have a way to tell where i am, roughly.
Of course, not only will I need a method of recording locations in a logic manner, I also have to worry about the accuracy of my readings, due to the limitations of my device/radio towers, possible weather conditions or even my physical location (valleys, cliffs, etc).
I should add that I'm looking for a very simple reproducible device here, not a standard GPS with loaded maps or the like. I'm fine with having a receiver and a notebook for locations, or just marking them down on a physical map. I don't know much about radios or GPS, I'm afraid, and would greatly appreciate any advice. Thanks!