Looking down you're eye sees details of known sizes, roads,
cars and houses. It is also able to see angles and
relations on the surface. Judging altitude from the air is
fairly easy. I always require my pre-solo students to fly
the traffic pattern [dual] with all the instruments covered.
I have them tell me their altitude and speed and then
uncover the instruments. They are always within 100 feet of
the correct altitude.

On the other hand, looking up, there are no references to
judge height. Is it a full size B52 or a model, is it 2
miles away or 25, the human eye /brain needs reference
points. But a trained observer is taught how to get those
references, such as the size of the airplane, the relation
of their thumb at arms length and the object, etc.



"Super Dave" wrote in message
ink.net...
|
| "Jim Macklin" wrote
in message
| ...
| GPS, even a $100 hikers model will solve the problem.
But I
| just say, look at the ground, you can judge 1,000 feet
| pretty well and you only need to apply the hemisphere
rule
| above 3,000 AGL.
|
|
| On the other hand, we always tell airport noise
complainers that it is very
| hard to accurately judge aircraft distances, such as
whether the plane is
| 500 feet or 1000 feet high.
|
|