"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.