[time-nuts] Positional accuracy of the M12+T

[Poul-Henning Kamp]

In message <459C2815.3070609 at xtra.co.nz>, Dr Bruce Griffiths writes:
>bg at lysator.liu.se wrote:

>A spherical error volume is a crude approximation, actually it =
>is an ellipsoidal with  as the height error is usually significantly =
>larger than the other positional errors which also may have different =
>rms errors. The errors are assumed to have a gaussian distribution with =
>different standard deviations for each coordinate axis.

The gaussian distribution is around the ellipsoides axis which
depend on the satellite constellation as seen from your point.

For the middle part of the plannet, measured in lattitude, a
NS+EW+Height ellipsoide can be assumed with good approximation.

But for a band closer to the poles, from roughly 66 to 56 latitude,
where we have no sats in half the plane and only occasionally pick
up signals across the polar hole in the constellation, the ellipsoide
actually isn't one, and its axis are not aligned with the coordinates
we care for.

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