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Re:London Underground hosts tests for 'quantum compass' that... by avianlyric on Tuesday June 18, 2024 @12:30PM (#40719643)
Yes, satellites are tracked by ground stations, and receive an update every 24 hours with information about their project positions in the future.

GPS satellites transmit this data in the form of an almanac which includes all the high level parameters for estimating the location of every satellite, and ephemeris data which allows you to calculate the precise location of the satellite, when used in tandem with the almanac.

The almanac doesn’t change too often, but ephemeris data is only valid for a few hours. The satellites recalculate the ephemeris data themselves, and normally have a few months of needed data stored on board, just in case they can’t get updates. But the expectation is they’re updated every 24 hours.

Re:London Underground hosts tests for 'quantum compass' that... by HideousKojima on Tuesday June 18, 2024 @02:53PM (#40720886)
This is also why, in a zombie apocalypse type scenario, GPS would become inaccurate past the point of usability within a few weeks, maybe a few months max.