9 ms·
Can't thoughtful discourse begin on a topic that is wrong, discussing why it is wrong? For example, I'd love to see a critique of what is wrong with: http://a
by flubert 6y ago
Can't thoughtful discourse begin on a topic that is wrong, discussing why it is wrong? For example, I'd love to see a critique of what is wrong with:
http://alternativephysics.org/book/GPSmythology.htm http://alternativephysics.org/book/GPSmythology.htm
...which makes the claim that you don't need to correct for relativistic effects for GPS to work correctly. I don't see an immediate, obvious flaw in his thinking, so I think it would be great to have as a conversation starter with someone more knowledgeable.
In fact, thinking about it more, doesn't stack overflow essentially depend on people being wrong and needing correction?
- AlotOfReading 6y agoThe author isn't actually familiar with how GPS works. First, there's no timestamp transmitted by the satellite (aside from the nav message, which isn't used for this). The satellite time is estimated as an offset from receiver time. Secondly, relativity is compensated for by fixing the satellite clocks so you don't get that location drift. Thirdly, if you had a perfect clock and used a naive algorithm, yes you'd have problems with changing elevation or gravity. Fortunately, GPS accounts for both receiver clock offsets (whatever their cause), and drift in offsets over time. The receiver is also constantly adjusting its clock based on the satellite signal so that error never accumulates beyond acceptable limits.