[ntp:questions] Motorola Oncore Surveyed Position

Chris Albertson albertson.chris at gmail.com
Thu Sep 8 00:23:36 UTC 2011

2011/9/7 Miguel Gonçalves <mail at miguelgoncalves.com>:
> 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.

Are both systems referenced to same "system".  WGS84 is the most
common one.   The earth is not a perfect sphere and over the years
cartographers have used different spheroids.  Using the wrong
spheroids can cause errors on the order of a few hundred meters

Rather then using Google a more reliable source is to download a USGS
Topographic map for your location. (they are all on-line now as PDF
files) These were all at one time ground checked by real surveyors.
The maps will have the locations for brass benchmarks that are set in
concrete.  It's fun to place your GPS on such a mark and see how close
it gets.
> 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 :-)
Chris Albertson
Redondo Beach, California

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