GPSD has a serious bug somewhere in its error modeling. What it effects is position-error estimates GPSD computes for GPSes that don’t compute them internally themselves and report them on the wire. The code produces plausible-looking error estimates, but they lack a symmetry property that they should have to be correct.
I need a couple of hours of help from an applied statistician who can read C and has experience using covariance-matrix methods for error estimation. Direct interest in GPS and geodesy would be a plus.
I don’t think this is a large problem, but it’s just a little beyond my competence. I probably know enough statistics and matrix algebra to understand the fix, but I don’t know enough to find it myself.
Hundreds of millions of Google Maps users might have reason to grateful to anyone who helps out here.
UPDATE: Problem solved, see next post.