"John Theune" wrote in message
news:Udo3g.5009$bU6.3635@trnddc06...
I'm somewhat surprised that no one has mentioned that both the Garmin
and Lowrance units that I'm familiar with have a page for satelitte
signal strength. I've never felt the need to run thru the 430/530 pages
to find a similar page but would not be surprised to find it buried in
there somewhere. To answer the OP's question it's there you just need
to read the manual to find which sub-menu it's on. If he's using a
non-aviation unit then all bets are off but again I would think it would
be there somewhere. Also on the units I use regularly the airplane icon
flashs on the main display when the signal is lost ala a pseudo RAIM
indicator

You are right all GPS software usually implements a satellite signal page.
It's not in any way shape or form what I asked for.

I want the GPS to take all of the inputs for number of satellites and signal
strength and derive from that just two integers:

1) Number of feet/meters of horizontal accuracy, within some confidence
interval (e.g., 99.95%)

2) Number of feet/meters of vertical accuracy, within some confidence
interval (e.g., 99.95%)

Those two numbers could become optional numbers for the primary display.
No one is forcing anyone to use them. If you want to simply trust the
instrument to give you a go-nogo decision, it's your life and if you feel
that is safe it's a free world (as long as you follow FAA rules ) so be
my guest.

For my personal taste, I understand that a GPS display is always an illusion
subject to different levels of inaccuracy. I am sensitive to the
difference between a display that is showing me accuracy to 10 ft, 100 ft,
or 1000 ft. In the original posted example the GPS was off target by more
than 5000 ft. Nothing on the original display gave me any clue that this
was the case. The two numbers I am asking for would communicate quite
succinctly that no one should rely on the display for anything other than
the most gross kind of positioning.

While I would love to see the feature I am looking for in any FAA-compliant
instrument like a Garmin 530, I think the feature becomes most critical in
non-FAA compliant GPS devices/software. The authors of such packages
cannot control the quality of the satellite antenna, or mounting, and
substandard GPS reception is probably a routine thing for PDA based GPS
devices/software. So finding a succinct way to communicate the accuracy of
the current signal in numbers that mean something to any user becomes quite
important. Making people look at satellite maps and signal strength seems
like a pure engineering exercise, and it doesn't collapse the input data
into a useful form.

--
Will