[EMAIL PROTECTED] wrote... > In article <[EMAIL PROTECTED]>, > Richard Eich <[EMAIL PROTECTED]> writes: > >If I were to set up five or six global locations, each time- > >synchronized to a local GPS receiver, how much variability would I > >expect there to be between the time as indicated by the GPS > >satellites used by each local GPS receiver. > > What decimal point are you interested in? > nanaseconds? microseconds? milliseconds?
0.500us > Are you interested in the time out of the GPS box > or the time out of an NTP server connected to a GPS box? The time out of the GPS receiver. The GPS receiver will be physically attached to the device to be sync'ed; no NTP. > How much money are you willing to spend? It always gets down to that, doesn't it? > The GPS side depends upon how fancy your gear is and how > good your antenna location is. The speed of light is > a foot per nanosecond. GPS position accuracy for consumer > gear is generally within a few 10s of feet so time accuracy > should be within a few 10s of nanoseconds. The national > standards laboratories use GPS to compare their atomic > clocks so you can get very very good if you work hard enough. > > With a bit of work, you can probably get a NTP server using > GPS to be within a few/10s of microseconds. That's good enough > so that you can easily measure asymmetries or jumps in network > routing. (assuming similar setups on both ends) > > Getting the time from a good NTP server to other systems gets > interesting. Thanks very much for your help. _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
