Does anyone have any "rule of thumb" method of estimating the altitude of our toys? I realise there are many technical solutions such as loggers and range-finders - which I don't have. It is also possible to program the birds not to exceed a given ceiling - but it would be helpful to discover if there was an easy empirical solution just using eyesight and some simple rules. Distance (range) could perhaps be roughly estimated using a simple home-made viewer with a selection of different-sized thumbnails of the quad - but you would have to do some in-the-head trigonometry to convert this to height. Why? - just for interest . . .