Sine and cosine of wind angle determination method

摘要

The wind angle determination method uses two concentric discs capable of relative angular movement. The first disc (1) which is transparent bears a wind angle rose (2) on it's perimeter and corresponding radii from it's centre (10). It is marked in degrees and also carries symbols enabling right angles to be easily sighted. The second disc (4) has two faces. The first face which is visible through the first disc has two circles (6) marked on it which share a common tangent with an arrow pointer. The circles have markings whose intersections with orthogonal radii on the first disc give the sine and cosine of the wind angle. The second face shows useful formulae and tables.