On Sat, 2007-03-17 at 01:51 +0100, Carlos E. R. wrote:
I thought you were using the data message from the gps unit to get both position and time stamp to use in your calculations, ignoring computer system time. At least, that's how I would try to do it.
GPS data over the serial port is non-deterministic. You cannot make reasonable time assumptions with it because it arrives when it arrives. If you want precise and current time, look at something like http://www.spectracomcorp.com/Portals/0/products/pdf/TSAT-PCI.pdf. It makes gps time available via the pci bus. This type of card eliminates problems with PC clock drift. Too bad the cards cost > $3000 USD. In addition, they charge $300 for the Linux device driver. OK. At least they support Linux. And, they charge the same for the Windows driver, so I guess they are at least consistent.
The system time without ntpd will surely drift, but constantly, no variation (hopefully). With ntpd it is supposed to be kept in sync with the "real world perfect time", but of course, you have to check if it is synced, and it will be slowed or accelerated now and then: thus variable drift.
This is our opinion as well. But it is a risky assumption. Any motherboard is free to have a bug.
I wrote a small description of how suse handles this. It was included in the old unofficial suse faq, somewhere in sourceforge, time ago. You might find it interesting.
I will look it up. -- Roger Oberholtzer OPQ Systems / Ramböll RST Ramböll Sverige AB Kapellgränd 7 P.O. Box 4205 SE-102 65 Stockholm, Sweden Tel: Int +46 8-615 60 20 Fax: Int +46 8-31 42 23 -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org