> I looked with Google ... and I got a picture of the dial... > It is an east declining sundial for local suntime and I > think the value is the declination of the dial.
That thought occurred to me too. In which case PL might be a slightly unusual use of the navigator's term Position Line? Strictly, a Position Line is the local arc of the circle centred on the sub-solar point that passes through the position you happen to be at. The plane of the dial stands on this arc when the outward normal to the plane is in the same direction as the sun. That is a good moment for measuring the declination of the dial which gives it some relevance. Maybe this is stretching the idea of a Position Line too far!! Frank King Cambridge U.K. --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
