[time-nuts] Survey plot as art.
Gary E. Miller
gem at rellim.com
Mon Jan 9 05:28:04 UTC 2017
Yo Hal!
On Sun, 08 Jan 2017 20:41:25 -0800
Hal Murray <hmurray at megapathdsl.net> wrote:
> gem at rellim.com said:
> >> The Adafruit receiver outputs NMEA format data. The lat/lon values
> >> are sent as dddmm.mm format (ddd=degrees, mm.mm=minutes) This
> >> restricts the resolution of the values.
>
> > Yes, easy to see the quantization in the Adafruit plot.
>
> Something doesn't look quite right. If the problem was as simple as
> reduced lat/lon resolution, I'd expect the output to be on a grid.
> Instead, what I see is more like a grid that was also missing 1 out
> of N slots. Where is that coming from? How do I predict N?
Yes, the raw data shows that it is not using all the possible
precision. It does skip lat/lons that are representable.
I'm almost at 45N, so that partlly explains why the lat missing codes
are smaller than the lon missing codes.
> I expect it's something like roundoff after the conversion from mm.mm
> to meters, or something like that.
No rounding happening in gpsd. That is in the raw NMEA.
> Just to make sure we are on the same wavelength, this is the graph
> I'm looking at.
>
> https://www.febo.com/pipermail/time-nuts/attachments/20170108/051ba89d/attachm
> ent-0003.png
Yup.
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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