In message <[EMAIL PROTECTED]>, Dr Bruce Griffiths writes: >[EMAIL PROTECTED] 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. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
