Yo Greg! On Mon, 10 Nov 2025 08:42:29 -0500 Greg Troxel <[email protected]> wrote:
> Another receiver, a ublox 7 GPS mouse.
> Poor fix still, same place. pAcc 30m.
>
> EPS usually ~6 km/hr. Flashing to 200 km/hr and then back.
> EPC 900 km/hr, while XYZ Vacc is ~2 m/s.
u-blox says to ignore EPS unless you are moving. They want you to look
at the dopler instead.
> I flipped to Imperial from the normal metric and see the same behavior
> in different units.
That is just a trivial unit conversion in cgps. Not gonna change anything.
> Again could be receiver, I'll also log the raw nmea and look at that.
Does not matter. gpsd uses the exact same equation that the u-blox does.
As mandated by the ICD. If the receiver sends it then gpsd uses it.
Otherwise gpsd calcualtes it.
This is probably way too much math:
https://ieeexplore.ieee.org/document/10848011
If you look, almost all the error estimates are based on math, with a
few inputs from the DOP, URA, etc. Ignoring all real noise sources.
But now that GNSS rceviers are doing things like carrier locking, and
tracking 160 sats at once, the actual accuracies are much better.
RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
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