Height Above Ground

in Vector Data
I found a lot of questions in the forum about how "height above ground" is calculated, but no answers. Has this been described somewhere I am missing?
Seems with LiDAR data there are a ton of points that show up below ground level with positive HEIGHT_ABOVE_GROUND values?
Thanks.
Seems with LiDAR data there are a ton of points that show up below ground level with positive HEIGHT_ABOVE_GROUND values?
Thanks.