>>>I have a NMEA GPS device that outputs the correct strings. However >>>due to where I have to position the device it doesn't always have a >>>lock on three satellites and then goes into Void mode. However the >>>time values are still being collected (It always sees at least one >>>satellite). > >>Which particular NMEA unit are you using? > > >>>Is it possible to write a parse (127,127,8,0) driver to read only the >>>time values and ignore the void message and thereby make it the >>>stratum 0 source? > >>If your unit is doing what I think it's doing, you probably don't >>want to do that. The GPS unit is telling you that it doesn't really >>know the time, but its best guess is xxxx. Why would you want to >>use time that's known not to be good? It would work OK if you >>didn't have to coast for very long. But then your PC can coast >>just as well for short times, maybe even better. > > IF you know your position, then a single satellite is sufficient to give > the time to high precision (ie, microseconds assuming you know your position > to 300m acccuracy). However, I suspect that your unit will not differentiate > between seeing no satellites whatsoever or seeing just one or 2. Many have an > on board oscillator which they use to interpolate between valid sightings. > Ie, it will depend entirely on your gps unit. > > > > _______________________________________________ > questions mailing list > [email protected] > https://lists.ntp.org/mailman/listinfo/questions >
Hi Guys I am actually using three seperate BU 303 GPS devices pointing in different directions. I know my position to within 10m (got from a roof reading with 9 sats in view) so my confidence in the readings is high. I only need accuracy to about half a second but then need that machine to be the stratum 1 server for the other machines in the environment. For reasons I won''t bore you with they can't connect to an external network connection so this seems the best solution? It's a shame no-one makes a GPS device that allows multiple sources at the same time (I suppose an old garmin GPS III plus unit with multiple external antennas I have might do it....if I could power it from the mains). Any other ideas? Thanks _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
