Why is altitude data complete fiction?

Former Member
Former Member
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...
  • Former Member
    0 Former Member over 10 years ago
    The problem is with the Virb not Virb Edit, this is the Virb Edit forum.
    I find the elevation is better if you switch the Virb on a while before you start recording to give the GPS a chance to calibrate the barometric altimeter, then turn the Virb off and then back on again and the elevation should be somewhere near correct.
    If you just turn it on and start recording the the GPS will be correcting the altimeter as you go and that can take half an hour before it sorts itself out.
    It would be much better if Garmin could just give us a way of calibrating the elevation at the start point.