In article ,
(Ron Lee) wrote:

I made another flight to KFTG this afternoon and periodically checked
the GPS receiver provided altitude versus my aircraft altimeter. GPS
was within 40' every time I checked (closer at times). I need to
check my last altimeter check to see if it has any errors but it is
certainly within standards so GPS is proving to be close enough for
VFR in these cold weather conditions.

Ron, is your GPS WAAS enabled?
My non-WAAS Garmin 195 will only get within 150 feet vertically.
Vertical is the least accurate of the three planes.