On Monday, July 18, 2016 at 1:43:19 AM UTC-4, 2G wrote:
There are errors in both methods of measuring altitude, as is discussed in:

http://www.xcmag.com/2011/07/gps-ver...nitive-answer/

The differences are substantial, as is discussed in:

http://www.icao.int/APAC/Meetings/20...20Altitude.pdf

One tends to think that GPS, being digital, is more accurate, but this is misleading. Myself, I would take the more conservative number (pressure altitude) and consider it an insurance policy. Final glides from that altitude are, by the very nature, long and subject to much error.

Tom

Excellent references; Thanks Tom!