Orientation method and appts. using solar shadow - relates direction of sun, time and cardinal points using three graduated circular scales mounted on gimbals

摘要

A circular plate which pivots around a horizontal dia. supported on the edges of a circular recess in a stand and containing a concentric disc rotable in its plane. The disc is equipped with the means to produce on itself a projection of the direction of the sun. The disc is divided into circular sectors centred on the point of rotation representing longitude and into concentric sectors representing time, one hour being equal to 15 degrees of longitude. The disc is turned through an angle corresponding to the longitude of its location in the direction of the suns rotation for easterly longitudes and inversely for westerly longitudes. The circular plate is pivoted w.r.t. the vertical at an angle to the latitude of its location and immobilised in this position. The direction of the sun and the time read on the disc coincide when the assembly is oriented correctly w.r.t. the cardinal points.