Reading the question of Rolf Menzl, [EMAIL PROTECTED] about declination of a wall.
For a plane, on which a dial has to be constructed we need to know the latitude, the declination and the inclination of that plane. If we do know these and we place a gnomon with length g perpendicular to the plane we can calculate the x-y coordinates of the shadowpoint of the tip of the gnomon for a certain date and (sun)time. This procedure can be used in reverse to determine the declination and inclination of a plane if we know the latitude, the date and (sun)time and the coordinates of a shadowpoint of the gnomon with length g. About this problem I held a lecture when I visited the conference of the British Sundial Society in Cambridge in 1991. This lecture with formulas is published in English in the BSS bulletin no 92.1 page 33 - 35. I myself learned this methode after a publication in the bulletin of De Zonnewijzerkring, (the dutch Sundial Society) in 1981. In this bulletin the procedure is published again in 1991 and 1992. (in dutch) This procedure gives two solutions for the declination and inclination, when using a single shadowpoint. By using two shadowpoints the wrong values can be elminated. This methode is uniform all over the world. I have no electronic version of this lecture to send with this message. Fer J. de Vries [EMAIL PROTECTED]
