Hi A GPS that uses position hold gets it's coordinates from one of two possible sources:
1) You measure the actual antenna location with a precision survey grade GPS and enter them. --or-- 2) The GPS does a survey for some amount of time. It averages it's own "reasonable" location estimates over this time period. With 48 hour averaging and a good sky view the location estimate can be pretty good. The position hold function allows the GPS to come up with a time estimate from a small number of satellites. This is useful when the sky view is not very good. A position error of one meter can translate into a time error of about 3 ns. Most GPS engines are rated for a 3 meter error, so that would be roughly 9 or 10 ns. Since the exact error depends on the stat's location relative to the error vector, the actual error will vary a bit (= it looks like noise). Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Wednesday, March 13, 2013 9:04 AM To: [email protected] Subject: [time-nuts] Is possible precise 1pps? I have GPS without "position hold", I wonder how precise 1PPS, which I want to use for disciplined OCXO. You do not know how GPS with "position hold" calculates the measured coordinates vs know the real coordinates of the expected error timestamps 1 pps? Thansk for information _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
