I went on a cruise from florida to mexico, and when we were in the middle of the ocean, i took out my cellphone, and it was obviously nowhere near a cellphone tower, you can tell this by the obvious marking in the phone that says you have ZERO bars. I loaded up Google Maps and I got a GPS lock in the middle of the ocean, showing my location...... This works because satellites continuously orbit the earth broadcasting GPS signals...
The same is true if you go into the middle of the Florida Everglades where there is ZERO cellphone reception..... and no cellphone towers anywhere near enough.... you can still get a GPS lock... and see where you are on the map...
Satellites orbit the globe of the earth.