On your garmin if you ever loose signal... look at your max speed. Either that or when I was sleeping at the wheel the runner hit 500mph!

It happened once, and I just thought it was a mess-up or something, but then it happened again, and I figrured it out.

 

Mine has never had that problem
I think you were just going 500mph.

 

You've got one fast Runner. My Garmin doesn't seem to do it, or I haven't noticed. I have the Garmin V, which one do you have?

 

Mine does it. It's a garmin legend.

 

I've hit 29,567ft altitude on little creek here in colorado with my old magellan. Probably same bit of twilight zone you guys are passing through.

 

my old garmin 12xl (circa 1996...) doesnt have a max speed...

 

My even older Garmin 12 (no XL) does have the max speed function. Never used though. I never trust that altitude function. I use the GPS on my boat, at sea level and it sometime shows altitudes of 450 to 500 feet.

 

My Garmin V has been pretty good on altitude. Ijust noticed that I never set it to show Max speed, maybe that's why I have never noticed it.

 

The garmin legend uses the satelites to figure out altitude, but the Vista uses air pressure to figure out altitude. The vista is more accurate. My watch shows altitude by using air pressure it'll show a difference when I walk up to my 3rd floor apt.