Stratum one autonomy and assumptions about GPS

[Gary E. Miller]

Yo Dan!

On Thu, 25 Aug 2016 10:23:50 -0500
Dan Drown <dan-ntp at drown.org> wrote:

> I had setup a test along these lines a week ago:
> https://blog.dan.drown.org/gps-pps-drift-when-it-has-no-signal/

Yeah, and I've been watching it.

> My results were a long term average of 250us-500us lost per day
> (~3-6ppb).  This surprised me because of how low it was, I assume I
> got lucky with the long term average temperature of the GPS module.

I do not believe your data.  After two weeks your GPS is still outputting
sat used data.  The Ephemeris timed out long ago, and the Almanac almost
gone too.  I think you still have a weak signal and since you GPS already
had a lock it is seeing something.

> Of course, this data doesn't apply to all GPS outage situations.

Nor does it reflect any test I ever ran.  But I admit to never testing
high end gear like Trimble gear.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588
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