John Rowland ("John Rowland" )
gurgled happily, sounding much like they were saying:

Mine does (BMW sat-nav), along with north/south etc. Not had much use
for it, but I guess it could be handy for figuring out if you're on a
flyover, or the road undreneath for navigation purposes.

And does it use the height information in conjunction with flyover
height information to work out which road you're on?

It's nowhere near accurate enough.

My Tomtom has a weakness here. You're heading from Central London to
Hanwell and it gives the correct route, turning off the A4 at one of the
junctions under the M4 elevated section. Then when you get beneath the
M4, it suddenly decides you have wrongly gone on the M4, and gives you a
new much longer route turning off the M4 miles away, with no clue about
which A4 junction you're supposed to use.

chuckle
And this, children, is just one of many reasons why GPS speed limiters
won't work.