On Wed, 7 Sep 2011, Chris Albertson wrote:
2011/9/7 Miguel Gonçalves <m...@miguelgoncalves.com>:
On 7 September 2011 05:07, unruh <un...@physics.ubc.ca> wrote:
> I've tried Garmin 18 LVC and Sure. Not want to start a war here but for
the
specifications and price Oncore beats both. :-)
Beats them how? What measurements have you made of those two units in
comparison with the oncore?
I am not disputing but would like evidence rather than mystical
feelings.
Simply read the manufacture's specifications. The most notable
I do not believe manufacturer's specs, especially not when they seem to badly
overstate the performance.
difference is the one sigma error on the time of the PPS. The newest
Oncore units (sold new by Synergy) are at the 2nS level while Garmin
Yes, and I simply do not believe this. Note that Oncore has claimed this
accuracy since at least 2003 ( ie old units).
claims 1uS. That is a 500X difference. The older UT+ version on eBay
I believe we were comparing Oncore to Sure, not Oncore to GPS18LVM
typically com in at about 55nS (one sigma) and these sell for under
$20.
55ns I might believe.
In the specific case we have here the Garmin unit lacks any PPS at
all. That is a HUGE difference.
No argument. But there the argument was not the PPS timing but whether or not
it met the OP's needs. It did. That is all that is required.
The other huge difference is the ability of the Oncore units to
self-survey their location, typically to within a third of a foot over
a 2 hour period. They then use this known fixed location in their
time solutions and greatly reduce uncertainty.
That may, or may not, be an advantage, depending on how they do it.
They use a binary protocol of the serial wire that dumps a lot of
detailed information and the timing is "good" bt not measured One
thing that comes over this bnary stream is the exact time relative to
UTC of the last pulse. And an error estimate. Som for example it
might say "xxx.00002314 plus minus 35nS" This is functionality not
present in any NMEA based GPS.
Agreed, but also irrelevant.
And I am confused. You were claiming that the pulses were within 2ns of utc,
and your example here is 23us out from utc. That is 10000 times different.
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