[ntp:questions] Motorola Oncore Surveyed Position
"terje.mathisen at tmsw.no" at ntp.org
Wed Sep 7 07:33:02 UTC 2011
Miguel Gonçalves wrote:
> Hi Terje!
> Thanks for your reply.
> I switched again to mode 4 and started again to see if I missed something. I
> believe I'll only have to wait 10000 seconds = 2 hours and 46 minutes... not
> much. :-)
> Unfortunatelly clockstats doesn't show position, only time. I believe this
> is because it's in position lock (0D?) mode. Here's a sample:
> 55810 40276.220 127.127.30.0 3524296275.999957838 2011 249 11 11 16 15
> rstat 08 dop 0.0 nsat 10,2 traim 1,0,1 sigma 77 neg-sawtooth -24 sat
> By the way... I was looking at the clockstats file and noticed that when I
> switched to mode 4 as I said earlier I got this
> 55810 40560.366 127.127.30.0 ONCORE: Loading Posn from SHMEM
> 55810 40560.367 127.127.30.0 ONCORE: Setting Posn and Time after Loading
> 55810 40562.091 127.127.30.0 ONCORE: Posn:
> 55810 40562.091 127.127.30.0 ONCORE: Lat = N 41.1745319deg, Long =
> W 8.6560764deg, Alt = 146.72m (481.36ft) GPS
> 55810 40562.091 127.127.30.0 ONCORE: Lat = N 41deg 10.4719m, Long =
> W 8deg 39.36458m, Alt = 146.72m ( 481.36ft) GPS
> 55810 40562.091 127.127.30.0 ONCORE: Lat = N 41deg 10m 28.32s, Long =
> W 8deg 39m 21.88s, Alt = 146.72m ( 481.36ft) GPS
> 55810 40564.365 127.127.30.0 ONCORE: Waiting for Almanac
> 55810 40567.365 127.127.30.0 ONCORE: Have now loaded an ALMANAC
> 55810 40567.365 127.127.30.0 ONCORE: state = ONCORE_RUN
> It seems this is my location... :-) Now you know where I live! :-)
> So the position is stored in the shared memory and when I reset the unit
> (mode 4) it uses the position stored in there.
> Anyone help care to comment this?
That seems like canonical behaviour, i.e. the way you want it.
As long as that position is within 3-5 m your timestamps will be within
10-15 ns, which is comparable to the inherent jitter in Oncore timing
For NTPD it is far better than you actually need, except TRAIM might
cause problems if you started with a position 300 m (1 us) off.
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
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