I fly with a Garmin Virb running version 4.00 of the firmware, and am using the newest version of Virb Edit. I'm a hang glider pilot, and fly the same site many, many times per month, so I know the altitude of the launch and landing sites - intimately...
But the camera is in La La Land where altitude is concerned. It's spot-on as far as position over the ground is concerned, but it's absolutely wacko on altitude. I don't even mean that it has trouble getting the altitude close - it's off by 800 feet or more when I turn the camera on at the launch and it occasionally tells me that I've only lost a couple hundred feet by the time I get to the landing - which is 1759 feet lower. Today it tried to tell me that I was gaining altitude when I was all but diving. And no, I wasn't in lifting air at the time.
There's no reason this should be the case. You can't get a position in 2-space with GPS without getting altitude to the same resolution. Oversimplifying a little bit, GPS is a triangulation process using multiple reference points (satellites) and measuring distance from those reference points instead of angle, as you would if you were navigating, on the ground, by landmark. I launch from the same place every time, and the map is always dead-on, within a meter or so. It's quite impossible to get position over the ground that accurate without similar accuracy in altitude.
What's going on with this? How has this not been fixed? I see posts from years ago, complaining about this same issue...