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moving to 8 digits of lat/lon (gpxlogger, maybe elsewhere)?

From: Greg Troxel
Subject: moving to 8 digits of lat/lon (gpxlogger, maybe elsewhere)?
Date: Thu, 03 Sep 2020 14:48:03 -0400
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (berkeley-unix)

I newly have an F9P, and have gotten it to work in RTK mode with the
MaCORS ntrip server, just by adding the ntrip:// URL with a mountpoint
for MSM, single base, specific station sort of nearby.  At least, the
"no RTK" light goes out, and the position wander as seen in josm
pointing to gpsd is very small, less than 1m p-p over a few hours,

I noticed that gpxlogger prints only 6 fractional digits of lat/lon.
This is 10cm, and I was seeing many adjacent samples with the same
values.  RTK receivers are making cm-level claims for accuracy, and
short-term stability may be better.

I would like tooling and data pipelines never to be the limiting factor
for accuracy in any analysis, so I'd like to change gpxlogger to use 8
digits, to be roughly 1 mm of precision.  I am not aware of any spec
reason that is prohibited or would cause trouble, and I don't expect it
to bother other people?

And, this is a general proposal that whenever anything in gpsd does
lat/lon, it uses %.8f, basically, and %.3f for height (in meters of
course, and hence mm).


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