mike regish writes:

Well, kind of. Most, if not all altimeters now, compensate for pressure
variations to show geometric (if that's the right term for it) altitude.

Not true. Altimeters show substantial differences with geometric
altitude as altitude increases. Air traffic control is based on
pressure altitudes, not geometric altitudes.

With SA disables in the GPS system, altitude is much more accurate than it
was. How accurate, I don't know.

GPS altitude can be from 200 to 500 feet off easily.

When I compare my altimeter with my GPS's,
they're usually about 100' apart. I'm not sure which is more accurate.

The altimeter is much more accurate.

--
Transpose mxsmanic and gmail to reach me by e-mail.