Universal solar chart shadow plotter and method for plotting a shadow

摘要

An apparatus for estimating a shadow on a scaled figure is presented herein. The apparatus includes a circular disk with a lines corresponding to the declination angle of the earth with respect to the sun at particular dates of the year. The apparatus also includes arcs on the circular disk which correspond to the earth's rotation at particular times of the day. The circular disk can also have a slot to facilitate insertion of a pencil or pen time therein. The circular disk is substantially transparent to enable a user to lay the disk over a scaled figure and make calculations and measurements corresponding to a shadow to be estimated. Also disclosed is a method for estimating a shadow for a structure depicted in a scaled figure. The circular disk is placed over the scaled figure such that the slot in the disk is aligned with an azimuth of the sun so as to trace a shadow line. The circular disk is then reoriented perpendicular to the shadow line so that a scaled height line may be traced. The circular disk is then relocated so that the center of the slot is located at the end of the scaled height line. The circular disk is then rotated to an angle corresponding to the height of the sun and a projection line is traced in the slot from the end of the scaled height line to the shadow line. In this manner, the length of the shadow for a given azimuth and altitude can be determined.