How to Spot Satellites | Space
GPS Next-Generation Operational Control System | Raytheon Intelligence & Space
Navstar Global Positioning System | navigation | Britannica
Satellite surveillance may be less of a privacy concern than you think -- for now - CNET
Satellite watching - Wikipedia
Since one satellite can see half of the earth, why do we need more than two satellites in a given network? | Science Questions with Surprising Answers
The Global Positioning System: Global Positioning Tutorial
Navstar: GPS Satellite Network | Space
Look up: It's a satellite! | Human World | EarthSky
Space debris: what can we do with unwanted satellites?
What is GPS? | NASA
What Causes GPS Signal Loss on Satellites like Swarm? - Eos
Feb. 14, 1989: GPS Enters Orbit | WIRED
How to Spot and Track Satellites - Universe Today
Satellite navigation - Wikipedia
SpaceX satellite signals used like GPS to pinpoint location on Earth | CARMEN UNIVERSITY TRANSPORTATION CENTER
Global Positioning System
How Do Satellites Keep Track Of Their Own Position?
What's the altitude of a typical artificial satellite, and how can I see one? | Astronomy.com
How is GPS used in spaceflight? | HowStuffWorks
How to Spot and Track Satellites - Universe Today
Reader on GPS positioning
GPS Satellite Display In Google Earth
