Yo Greg! On Sun, 09 Nov 2025 20:01:59 -0500 Greg Troxel <[email protected]> wrote:
> EPX/EPY/EPC are 10/10/20 m. That's bad, but poor signals indoors and
> seems reoasnable.
> EPS/EPC are 83 km/h and 167 km/h. That's bonkers.
[...]
These are from the GPS, unless the GPS does not provide them. The
algorithms are specified in the ICDs, and do not reflect current reality.
> So, it would be good if people could look at their EPS/EPC and see if
> they are sane compared to the EPX/EPY/EPV.
The equations to derive one from the others are standard. Which means
the receiver can't add any black magic to get them to correlate to
reality.
The eqaations are set in stone, but what they mean is not. Do they me
an the real position is within those bounds 50% of the time? one sigma?
two sigma? three sigmas? 95%? 95? 1%? So totally meaningless.
This should be an FAQ. For some reason people think they mean something.
> Note that EPX/EPY/EPV are really EP(lat), EP(lon), EP(HAE).
Yeah, confusing. Decumented in include/gps.h and man gpsd_json. And
directly taken from the receiver's data, when available.
u-blox recently added the Error Ellipse message. That actually migh be
useful.
RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
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