virig wrote:
All satellites are rotating following their orbits, so you can
estimate the best time in your area to have more satellites with more
strength...
http://personaltechinfo.googlepages....t_accurate_gps

My Garmin 150 has always had a "GPS Plan" mode where you can specify a
time span in the present of future, for which it will say when accuracy
is poor. I just checked my home airport for 31 Oct'07. The reuslt was
that accuracy will be poor (no 3D) from 4:07-4:47 then. It's been in
the built-in software from the get-go, using contempoaneous epheris
information.

Ang. C.