Any suggestions for a good GPS?

[inactive]

I have an iPhone 5S currently, and it has location services like most do, but don't they rely on cell tower pings for location? My iPhone 4 across the panhandle of OK, and in the mountains west would give me a notification that location services were not available and travel info would come from memory. Google maps.
My Tom Tom and Garmin hand held continue to update real time unless satellites are blocked by mountains.

Your phone will work just like those GPS units with an app that has offline maps loaded. For example the $50 garmin app (I only know it because my employer had provided s license for it at one time). Again, the location is derived from satellite GPS. Cell signal is only needed for the Google and Apple maps tool as the maps themselves.