GPS & Relativity: Position Error Lower Than 38000 Feet?

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    Gps Relativity
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SUMMARY

The discussion centers on the relativistic effects on GPS satellite clocks, specifically the claim that without compensation, GPS would generate a positional error of 38,000 feet per day. Participants argue that this estimate is flawed because GPS receivers continuously synchronize their clocks with satellite signals, mitigating any potential error accumulation. The consensus is that the relativistic effects are compensated effectively, resulting in a much lower positional error, estimated at approximately 8.9 mm, which is negligible for practical applications.

PREREQUISITES
  • Understanding of GPS technology and its operational principles
  • Familiarity with relativistic physics and time dilation concepts
  • Knowledge of clock synchronization methods in satellite systems
  • Basic mathematical skills for calculating positional errors
NEXT STEPS
  • Study the principles of GPS time synchronization and its impact on positioning accuracy
  • Learn about the effects of relativity on satellite systems and clock adjustments
  • Explore the mathematical calculations involved in GPS positioning, including relativistic corrections
  • Read the paper on relativistic time shifts in orbital and ground-based reference frames for deeper insights
USEFUL FOR

Students of physics, engineers working with satellite technology, and professionals involved in GPS system design and optimization will benefit from this discussion.

  • #61
Even atomic clocks are not perfect. If they were then I think the OP would have been right. For everything to stay synchronized the clocks on each satellite must re-synchronize from time to time with a master clock. The master clock is ground based so if relativistic effects were not compensated for then a satellite that just had its clock synchronized would be out of sync with a satellite that had been synchronized less recently. having satellites out of sync would certainly cause error, though I don't know how much.

http://tycho.usno.navy.mil/gpsinfo.html

Also, the GPS system is designed to provide 4 co-ordinates, not 3. The 4'th being time. If the master clock were space based and time dilation were not accounted for the time co-ordinate would drift. A cheap receiver with a fallible clock would not know how much drift to account for.
 
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