I am not a pilot and have come to this site to ask a question about the measurement of height. This is as a result of the comments made as a result of a question in the Physics Stack Exchange forum "Does barometer improve gps accuracy?"
I feel that there will be more of you on this site who have real time experience with flying and so can answer my question which is:
Which is more accurate for height measurement: GPS or barometer?
I have noted that those engaged in geocaching often have GPS units with built-in barometers to improve height accuracy.
One of my friends who is a pilot responded as follows:
A light aircraft relies on a barometer that is set to the standard 1013 millibars when in cruise at height (or the regional QNH when lower) but they set to the local reading for the airfield (QFE) when planning their decent. Commercial aircraft also have ground proximity radar but they also have a standard set of old fashioned flight instruments in case the electronics fail. My old aircraft GPS did indeed read out height as well but you were told never to rely on it!