On Nov 22, 8:45 pm, "William Bruce" wrote:
I've just bought a TomTom GPS for my car with preloaded road maps of the US
and Canada. My question: Will it work in my 172 at 3,000 to 5,000 feet,
showing the roads below, etc?

I have tried Tomtom (on Dell AXIM) on an airplane and it doesn't work.
It will get a fix of your position, and you can watch yourself fly
across roads, lakes and rivers. But you can't ask it to navigate
anywhere. In order to compute a route, you have to stand still for a
while (for long routes this could take a couple of minutes). In the
very least you should stay on one road while it is computing. Since
you are obviously not doing any of this while flying, the program will
never finish computing the route. My screen just said "computing
route" with a progress bar for a very long time. When it seemed like
it was getting close to the end, it would start all over again, and
the cycle never stopped. My guess is by the time it computed a route,
we were far from that position and an entirely new route had to be
computed. This may also have something to do with the processing
speed of the Dell AXIM. However, even if you ran this on a faster
platform, it might still be constantly recomputing a new route because
you are obviously not following any of its suggested routes. One
possibility is to fly over a highway in a sparse area, and it may be
fooled into thinking that you are actually on that road. But that
might also be hard to do because it is quite sensitive to your
position. If it thinks you are off the road, it is going to start
recomputing again. It was fun trying it, but I can't see how this can
be made to work.

If you really need to find a street while flying, the best approach is
to insert the lat/lon co-ordinates into a regular GPS.