[TowerTalk] ASL vs HAAT

[Jim Jarvis]

As Dave Robbins pointed out, topo maps indicate altitude ASL.
So do aeronautical charts.  It's easier to talk about the 
printed numbers, than it is to calculate height above average
terrain...which almost certainly will vary, based on azimuth.

And then, there is the question...why 5,000 or 8,000 asl?
The answer is....there's RF up there than never gets down
to the flatlands!   (or so the lore goes.)  :)

N2EA
jimjarvis at ieee.org