[ntp:questions] Motorola Oncore Surveyed Position

Miguel Gonçalves mail at miguelgoncalves.com
Wed Sep 7 09:20:26 UTC 2011


Hi Terje!

Thanks!

My Oncore reported 146 m altitute but I checked with Google Earth and with
my iPhone and my altitude at this location should be 75 m. I am using 75.
It's working fine since 20110907T2300Z.

I will let it run for a few days and plot some graphs and share them with
the list.

Yes... I know Oncore performance (and even Garmin 18, 18x and Sure) are more
than enough for NTP but I am a time freak, pardon, nut :-)

Cheers,
Miguel

On 7 September 2011 08:33, Terje Mathisen <"terje.mathisen at tmsw.no"@
ntp.org> wrote:

> 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
>> 35000080
>>
>> 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[0]: Loading Posn from SHMEM
>> 55810 40560.367 127.127.30.0 ONCORE[0]: Setting Posn and Time after
>> Loading
>> Almanac
>> 55810 40562.091 127.127.30.0 ONCORE[0]: Posn:
>> 55810 40562.091 127.127.30.0 ONCORE[0]: Lat = N  41.1745319deg,    Long =
>> W   8.6560764deg,    Alt = 146.72m (481.36ft) GPS
>> 55810 40562.091 127.127.30.0 ONCORE[0]: Lat = N  41deg 10.4719m,   Long =
>> W   8deg 39.36458m,  Alt =  146.72m ( 481.36ft) GPS
>> 55810 40562.091 127.127.30.0 ONCORE[0]: 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[0]: Waiting for Almanac
>> 55810 40567.365 127.127.30.0 ONCORE[0]: Have now loaded an ALMANAC
>> 55810 40567.365 127.127.30.0 ONCORE[0]: 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
> receivers.
>
> 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
>
> --
> - <Terje.Mathisen at tmsw.no>
> "almost all programming can be viewed as an exercise in caching"
>
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