Last time I drove across Tennessee, I could not get a GPS lock for most of the state. I had a navigator and both myself and my son had cellphones, yet none of the three devices could tell us where we were. Why do the "satelites" pick and choose where they will work?
No, they probably pick and choose
who they work for.
These new "Smartelites" sense whether or not the user believes in satellites
.
But, more seriously I can't explain your problems.
I can say that I have various GPS units, mainly Garmin, starting with a Garmin
etrex VISTA (in 2002) to my current Garmin
nuvi 3790 - bit long-in-the-tooth now.
I have travelled over a large part of inland Australia, in many cases hundreds of miles from any mobile phone services. The GPS units worked everywhere.
I also had a satellite phone but did not use it much (cost $2.00/min a lot then), but the few times we did need it we certainly had service,
except once!We were right at the tip of Cape York (yes GPS worked fine
but![1]) and we thought we'd be smart and took the bulky Sat phone, so we could call our folk and say we were calling from the top end of Australia!
That fell flat! THE Sat phone took 20 minutes to find a satellite and others in the group had ordinary CDMA phones and had signal from Bamaga! Checking later we found that the northern part of Cape York was outside the footprint of the Globalstar satellite we were using in 2003, so yes, I am sure that the the satellite phone did not get its signal from those phone towers!
[1] The
but is that the GPS coordinates dud not agree with the coordinates on the marker post at the tip of Cape York. They were using the previous WGS84 datum, but the GPS was. Traps for new GPS users, though modern maps would use the modern mapping reference.