GPS Trivia Questions

GPS signals are weak radio waves and can't penetrate concrete, metal, or thick walls. Indoors or tunnels, signals are blocked or reflected, causing loss of accuracy.

Each satellite continuously sends its own position and precise time. Your device uses the time delay of signals from at least four satellites to triangulate your location.

GPS is a one-way system: satellites only broadcast, and receivers only listen. Your device never sends signals to the satellites; it just computes its own position.

The baseline constellation is 24, but there are often 31 or more active satellites. Spares ensure coverage if one fails, and more improve accuracy.

GPS was created by the U.S. Department of Defense for military navigation. Civilian use was allowed later, with intentional signal degradation until 2000.

Each satellite completes two orbits per day in a medium Earth orbit at roughly 20,200 km altitude. This ensures at least four are visible from any point on Earth.

Satellites move fast (special relativity) and experience weaker gravity (general relativity). Without correcting for these, GPS would drift about 11 kilometers per day.

Each satellite carries multiple atomic clocks with accuracy to nanoseconds. A one-second error would cause a position error of about 300,000 kilometers.