[ntp:questions] Motorola Oncore Surveyed Position
"terje.mathisen at tmsw.no" at ntp.org
Thu Sep 8 08:28:35 UTC 2011
Miguel Gonçalves wrote:
> Hi Terje!
> 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.
There are two heights!
The real ASL height, which is what you get from a local topo map, and
altitude above the GPS geoid, which can be significantly higher or lower.
I.e. check the type of altitude!
> 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 :-)
> 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.
>>> believe I'll only have to wait 10000 seconds = 2 hours and 46 minutes....
>>> 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
>>> 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"
>> questions mailing list
>> questions at lists.ntp.org
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
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