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
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@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
pgpEQi7T8mkHT.pgp
Description: OpenPGP digital signature
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