How GPS finds you: satellites, clocks and Einstein

How a phone that only listens works out where it is: satellite clocks, travel times, four spheres, the errors that creep in, and Einstein's correction. Your phone can put a dot on the map to within a few metres without sending a thing. This Marker Machines film follows the whole chain on one big whiteboard: just over thirty GPS satellites in six orbital rings, each carrying atomic clocks and broadcasting its time and position; the radio signal falling to your phone at the speed of light; the travel time turned into a distance; spheres that narrow your position to a circle, then two points, then one; and the fourth satellite that fixes your phone's cheap clock. Then the ground stations that keep the satellites honest, the ionosphere, weather, city reflections and satellite geometry that blur the answer, and the relativity correction without which GPS would drift by more than 11 kilometres a day. It ends with the tricks that sharpen a fix today, two frequencies, augmentation systems and other constellations such as Galileo, GLONASS and BeiDou, and one sweep across the finished board. Watch it with its sources on SkillBay: https://skillbay.dev/wiki/marker-mach... Chapters 0:00 A phone that only listens 1:01 Satellites in six rings 2:00 Clocks that broadcast the time 3:13 Turning time into distance 4:25 Sphere, circle, two points 5:16 The fourth satellite fixes the clock 6:28 The keepers on the ground 7:19 What slows and bends the signal 9:18 Einstein in orbit 10:40 Sharper fixes 12:05 The whole chain Narrated by Todd, an ElevenLabs voice. Music: "Moving parts", made for Marker Machines with ElevenLabs Music. Every frame is drawn by SkillBay's whiteboard-explainer-film skill: https://skillbay.dev/skills/whiteboar... Sources Space Segment, GPS.gov, National Coordination Office for Space-Based Positioning, Navigation, and Timing (2023): https://archive.gps.gov/systems/gps/s... Control Segment, GPS.gov, National Coordination Office for Space-Based Positioning, Navigation, and Timing: https://archive.gps.gov/systems/gps/c... GPS Accuracy, GPS.gov, National Coordination Office for Space-Based Positioning, Navigation, and Timing: https://archive.gps.gov/systems/gps/p... GPS Augmentation Systems, GPS.gov, National Coordination Office for Space-Based Positioning, Navigation, and Timing: https://archive.gps.gov/systems/augme... Other Global Navigation Satellite Systems, GPS.gov, National Coordination Office for Space-Based Positioning, Navigation, and Timing: https://archive.gps.gov/systems/gnss/ GPS Operational Advisory 277: GPS status 04 Oct 2026, U.S. Coast Guard Navigation Center (2026): https://content.govdelivery.com/accou... Relativity and the Global Positioning System (Neil Ashby), Physics Today 55 (5), American Institute of Physics (2002): https://physicstoday.aip.org/features... What is GPS?, NASA Space Place: https://spaceplace.nasa.gov/gps/en/ Space Weather and GPS Systems, NOAA Space Weather Prediction Center: https://www.spaceweather.gov/impacts/... 5.3 GPS Error Sources (GEOG 160), Penn State College of Earth and Mineral Sciences: https://courses.ems.psu.edu/geog160/b... 2.8: The Global Positioning System (Introduction to General Relativity), LibreTexts Physics, Skidmore College course: https://phys.libretexts.org/Courses/S... Inherent Limitations of Smartphone GNSS Positioning and Effective Methods to Increase the Accuracy Utilizing Dual-Frequency Measurements (Yun, Lim, Park), Sensors 22 (24), MDPI (2022): https://pmc.ncbi.nlm.nih.gov/articles... Error analysis for the Global Positioning System, Wikipedia: https://en.wikipedia.org/wiki/Error_a... Wide Area Augmentation System, Wikipedia: https://en.wikipedia.org/wiki/Wide_Ar... More from the SkillBay Wiki Chalk & Reason:    / @chalkandreason   Lamp & Shadow:    / @lampandshadow   Corkboard Files:    / @corkboardfiles   #HowItWorks #Engineering #MarkerMachines