Pilot's Tip of the Week

Altimeter vs. GPS Altitude

Featuring John Krug

Subscriber question:

"Under VFR, my altimeter displays one altitude while my GPS displays a different altitude. Which one do I use?" - Wayne P.
Press to play audio


"Under VFR, you should be flying at a cardinal altitude (odd or even thousand-foot altitudes e.g. 4,000, 5,000, 6,000, 7,000, etc.) plus 500 feet. This provides separation from IFR aircraft and other VFR aircraft on crossing courses.

GPS AltitudeYour altimeter displays indicated altitude and this is what you should always use (for traffic separation). Indicated altitude is pressure altitude corrected for local atmospheric conditions. The correction is done by entering the altimeter setting given by Air Traffic Control or on an AWOS.

All aircraft in a given area should be on the same altimeter setting so relative (altitude) separation is maintained.

A GPS, on the other hand, measures your absolute altitude off several satellites. While more accurate than pressure altitude, it does not provide the same relative separation from other aircraft (since all aircraft are using indicated altitude)."

Next week's tip: Estimating crosswind

Scenic VFR Flight Using X-Plane 

Watch this end-to-end VFR flight using X-Plane. The graphics, scenery and realism of the latest software are stunning. See the pilot plan his route and configure the airplane, weather, etc. He uses radios, GPS and ForeFlight like you would in a real plane. This video demonstrates the training benefits you get with a good sim. Watch it here…