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: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
