[time-nuts] Survey plot as art.

Gary E. Miller gem at rellim.com
Sun Jan 8 16:52:08 EST 2017


Yo All!

I just ran 24 scatter plots on 2 GPS with external antennas one inch apart.

pi2-5.png is an Adafruit GPS HAT with an MTK-3301. upuv2.png is an
Uputronics GPS HAT version 2, with a uBlox 8.

See attached.  I'm not sure it sheds any light on this discussion...

There does appear to be a bit of correlation between the bigger random
walks in the graphs.  And a whole lot of other things going on.

During that time, the Adafruit saw 6 to 12 sats and a constant TDOP of
0.82.  The Uputronics reported seeing 4 to 20 sats and a TDOP from 0.42
to 32.6 and a mean of 0.786 and a SD of 0.668.

To bring this back to time-nuttery, when the TDOP hit 32.6 I can see a
2 micro Second spike in NTP jitter.  So for that small period in time
my Raspberry Pi clock was more stable than my PPS.

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

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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