I would venture to say you can’t do better than hearing it from the inventor himself!
How GPS Works
Basic APRS – An Introduction
(Click link above for the ARRL APRS webpage explaining APRS)
“Official U.S. Government information about the Global Positioning System (GPS) and related topics”
GPS Modernization Video
GPS is getting an $8-billion upgrade
“Without it, ATMs would stop spitting out cash, Wall Street could blunder billions of dollars in stock trades and clueless drivers would get lost.”
New Satellites Could Make GPS Harder to Jam
“Without GPS, drones can’t fly, communications networks can’t function, and you don’t have a chance of figuring out how to get to your Aunt Sadie’s place in New Jersey. And right now, GPS is highly vulnerable because its weak signals are coming from an aging constellation of satellites.”
How GPS Receivers Work
“Our ancestors had to go to pretty extreme measures to keep from getting lost. They erected monumental landmarks, laboriously drafted detailed maps and learned to read the stars in the night sky.”
Check out the Air Force Collaboratory:
How Collaboration Leads To Great Ideas
How Robots Help Search And Rescue Teams
Voyager 1: Where To Next?