Originally Posted by
hamster
It should be very easy to test. If Garmin normally measures stagnation pressure (as mounted on the bike), it has to do velocity correction. If it does velocity correction, it should immediately show up as a jump in elevation if you turn it on inside a car that accelerates from stand still to the freeway speed (you may need to crack rear windows to equalize pressure).
What does happen on the 510 on occasion is on a headwind climb it goes seemingly bonkers and jumps to something ridiculous, like a 35% or 50% grade, then slowly reduces back to something sane. I assume this is when it's so off the GPS altitude that it triggers an altimeter reset. Curiously, this never seems to show in the post-ride data. Maybe it's identified heuristically as junk data and ignored.