Markus Wichmann

Hi! To get this exactly you have to use a radar altimeter - most military acr use this to perfom low altitude flight, e.g. the Tornado has this instrument linked to the flight guidance system to follow the terrain in extrem low altitude at high speed (100 ft.) - perhaps ther is a gps that has the altitude data linked with the pressure altitude and that shwos you the differenez or you can do this for yourself by using charts with altitude data. Regards, Markus