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You need a ruler and a thin line. Reading the ruler in millimetres it will be up to 90% accurate.

How it works

It is the principle of three even sides of a triangle. You can read lying down or standing up. Have the line round your head fastened to the ruler with a distance of approximately 40 centimetres from eye to ruler. We see the flight height (H) and given wing span (S) an eye distance to ruler (e) and the measured wing span (S) on the ruler. For example – the model wing span is 2450mm and the distance from eye to ruler is 430mm. Read the wing span from the plane on the ruler. If this is 4mm then the flight height is (2450 x 430) / 4 = 263375mm = 263.4m.

It is not an altimeter but your distance is between 250 – 275m. It is more accurate than just guesswork. Try it and have lots of fun.

By Cor Klos – Wednesday 18 February 2009

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