Hi Tom, IMHO in your point "2)" you should not mirror the -104 to +104, but add 180 degrees instead resulting in a final longitude of +76 after 12 hours. In all other respects I agree. Peter
Am Dienstag, 24. Mai 2016 schrieb Tom Van Baak : > Hi Skip, > > > Any help in understanding this behavior? Thanks in advance. > > Yes, GPS satellites do repeat every ~12 hours in orbit around the mass of > the earth -- but -- you and the earth turns 180 degrees during those 12 > hours. So you're no longer where you should be when the 1st repeat occurs. > Instead you have to wait yet another 12 hours for the earth to get back to > the place where you were, in time to see the 2nd repeat. Now when you hear > "get back, get back, get back to where you once belonged", you'll think of > GPS satellites instead of the Beatles. > > So the LH plots are correct. Here's another take: > > 1) Say it's 6 PM MDT in Denver at lat/lon +39/-104 and you see a pattern > of N satellites in the sky. > 2) Tomorrow morning at 6 AM MDT that same pattern will be in the sky -- > not for you -- but for some guy at 6 PM lost in Inner Mongolia at lat/lon > +39/+104. > 3) Tomorrow evening at 6 PM MDT that same pattern will again be in the > sky, this time for you in Denver. > > /tvb > > ----- Original Message ----- > From: "Skip Withrow" <skip.with...@gmail.com <javascript:;>> > To: "time-nuts" <time-nuts@febo.com <javascript:;>> > Sent: Monday, May 23, 2016 3:43 PM > Subject: [time-nuts] I thought GPS repeated every 12 hours (-2 minutes) > > > > Hello Nuts, > > > > I am attaching a capture from Lady Heather of a 3-day run. You can see > the > > temperature vary by 7C over each day. The TB is being run open loop and > > another GPSDO 10MHz input to the unit instead of the unit's oscillator. > > > > I expected the purple line to repeat every 12 hours based on the GPS > > constellation being the same (which maybe it kind of does), but there is > > definitely a 24 hour repeat. What is really weird is that the number of > > satellites that LH sees also repeats on a 24 hour cycle, not 12 (bottom > > trace). > > > > Any help in understanding this behavior? Thanks in advance. > > > > Skip Withrow > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com <javascript:;> > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.