Aren't people missing the point? An altimeter is a pressure instrument and depending on what is set on the subscale, will read pressure heights relative to that setting. In the UK we are supposed to fly cross country (when below the transition altitude) with a regional QNH set. This is a value which should ensure we are always no lower, and usually a bit higher than the reading on the altimeter so we don't fly into things. The altimeter is reading a pressure altitude, not a true altitude.
Last edited by Andrewgr2; 3rd April 2016 at 05:53.
Reason: Correct typo