Good Morning everybody. I hope that this thread is of interest. I am a retired architect with an interest in Mathematics. My picture shows a view of The London Eye. We know that it views as an ellipse but the major axis (drawn), clearly is not at right angles to the axis of the wheel and if you "walk up" the centre of vision this angle will not change, so it bears no relation to the vanishing points of say, a bounding square. I cannot find any information on this matter on line apart from the mundane methods of drawing an ellipse. Is there any established method of calculating this angle when the angle of view, in both planes are known?