GPS & Relativity: Position Error Lower Than 38000 Feet?

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    Gps Relativity
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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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