Help estimating altitude without altimeter?

If you can estimate the distance and judge the angle, this fixes the
height - this is simple trigonometry.

In the UK we teach an exercise called the zig-zag circuit where the
instructor demonstrates a circuit starting at the right high key
distance, height and angle to the reference point, but allows the
gider to drift in so the low key point is reached at about the right
height, but much too close in. Thus the student can see that the
angle looks much too steep (the impression given is that you are much
too high, but you are not). Then you move back out until the angle
looks right and complete the circuit normally.

I do not disagree with ZZ that regular experience of what a circuit
should look like is a necessary part of training. Also learning to
judge what items on the ground, such as trees, vehicles and houses
look like from different heights.

Derek Copeland

P.S This is posted from Google Groups, as I can't seem to access
r.a.s. directly from gp.net. Is there a problem with my email address
or UK postings Andy?