gem@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? I expect it's something like roundoff after the conversion from mm.mm to meters, or something like that. 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 -- These are my opinions. I hate spam.

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"If you can’t measure it, you can’t improve it." - Lord Kelvin

Yo Hal! On Sun, 08 Jan 2017 20:41:25 -0800 Hal Murray <hmurray@megapathdsl.net> wrote: > gem@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@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