Global Positioning System (GPS)
GPS is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force.
Segments: 1. Space (Satellites). 2. Control (Ground stations). 3. User (Receivers). Signals: L1 (Civilian), L2 (Military/Dual), L5 (Safety-of-life).
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🧒 Explain Like I'm 5
Imagine you are lost in a forest. Three of your friends stand in different spots far away and shout 'Coo-eee!' at the same time. Because of how long it takes for the sound to reach you, you can tell which friend is closest. If you know exactly where they are standing, you can figure out where you are. GPS is just your phone doing this with satellites instead of friends.
🤓 Expert Deep Dive
Technically, GPS works via 'Trilateration'. Each satellite transmits a 'Navigation Message' containing its 'Ephemeris' (precise orbital path) and 'Almanac' (general health and position of all satellites). Receivers use a 'Pseudo-random code' to time the signal's arrival. A major challenge is 'Atmospheric Delay'—the Ionosphere and Troposphere slow down the signal, causing errors. 'Assisted GPS' (A-GPS) helps phones lock onto satellites faster by using cell tower data to get the Almanac via the internet. For high-precision needs like surveying, 'Differential GPS' (DGPS) or 'RTK' (Real-Time Kinematic) uses ground-based stations to correct errors down to the centimeter level.