On Tuesday, January 14, 2014 11:47:31 AM John Andersen wrote:
NTP will often NOT compensate for several hours of difference.
This is a worry. These systems are in vehicles on the road. We have no control over the time on the PC clock at boot. We do NOT (repeat NOT) want the users entering the BIOS and mucking about.
This is by design, but, there may be a switch to over-ride it. When it does get a connection to NTP, even after weeks of being disconnected or turned off, it will sync immediately, and adjust time all at once, provide the clocks are reasonably close. When I say immediately, I mean as soon as NTP elects a clock from the list you provide to it.
I don't recall any gradual time shift, but I haven't read the man page in a while.
Your GPS source should provide you UTC time. (Well, US GPS sats provide GMT plus an offset to arrive at UTC, but Glonas and Galileo only provide UTC).
However, I've seen many references on the net about GPS being a poor source, probably due to the delay in getting time as you mentioned. It might be wise to not start NTP until you have believable time from the GPS.
As it turns out, we want to set the time because we time stamp everything. And the way we hook all the parts together is by location as provided by the GPS. So, what we really are after is having the PC clock match the GPS time as closely as possible. How that relates to some global correct time is not really interesting. I should add that our GPS are really inertial navigation systems that have the GPS as one source to maintain location. There are also inclinometers, gyroscopes and distance measurement devices as well. INS systems use the GPS time to time stamp locations. -- Yours sincerely, Roger Oberholtzer Ramböll RST / Systems Office: Int +46 10-615 60 20 Mobile: Int +46 70-815 1696 roger.oberholtzer@ramboll.se ________________________________________ Ramböll Sverige AB Krukmakargatan 21 P.O. Box 17009 SE-104 62 Stockholm, Sweden www.rambollrst.se -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org