40 ms·
Thank you. Is it fair to say that the 38µs correction done in the satellites is more for GPS’s other use? That is, as a source of accurate timekeeping to the re
by function_seven 10y ago
Thank you. Is it fair to say that the 38µs correction done in the satellites is more for GPS’s other use? That is, as a source of accurate timekeeping to the receivers? It sounds like positioning is not affected like I thought, but the designers felt the need to engineer a solution to the relativity problem nonetheless.
- dogma1138 10y agoThere are different corrections for relativity, one is the "one time adjustment" that all clocks got which is on average closer to earth clock rates but it's not 100% constant since general and special relativity do not affect all satellites in the same manner and they all got the same clock correction. The other "relativistic" correction is one done in the receiver and is needed for geometric range delay calculation, basically taking into account that light doesn't travel in a straight path, we've kinda known that since the early days of classical optics - Fermat's principle or the principle of least time. Now while it's true that we are using the "relativistic" version of this in our calculation solving the classical or even ignoring it all correctly as long as we account for other effects would still allow you to find a starbucks. Since GPS was initially intended for military use it had other uses such as time keeping that can be used to synchronize communication, encryption and other things these errors can be cumulative whilst navigation errors are often not since the drift would be more or less uniform with all satellites you see.