Is there any way to have the Garmin 430/530 put its current display accuracy
on the primary display as an ongoing statistic, based on the number of
satellites in view? How, in general, do the Garmin units notify you of
situations where GPS accuracy has been compromised to a level that makes it
unsafe to use the Garmin for a GPS approach?

I got an interesting lesson in GPS recently while traveling with a handheld
GPS as the passenger in a plane. The GPS showed us landing about two miles
east of the airport. I figured out only later that the position of the
antenna was such that many satellites were blocked, so the accuracy of the
GPS signal was greatly diminished. The particular software I was using
didn't display its current accuracy on the primary display. Based on that
event, I realize I cannot just trust a GPS display without first
understanding the current accuracy of the signal.

What would be really nice is if the primary display would show vertical and
horizontal accuracy as two separate numbers, based on some high confidence
interval (99.99+%). Knowing that the current display reading is accurate
to 10 ft vertical and 15 ft horizontal, for example, might make you a lot
more comfortable in following a GPS approach than a display where the 99.99%
confidence interval is 2000 ft vertical/horizontal (i.e., GPS reliability is
completely compromised by virtue of blocked satellites, bad GPS antenna,
etc).

--
Will