Sundial for telling solar time and clock time across a range of latitudes and longitudes

Abstract

A sundial for telling apparent solar time and clock time across a range of latitudes and longitudes. A solar dial is formed with an index point and a noon hour point. A plurality of concentric latitude indicia are centered at the index point and at least one map indicium is overlaid by the concentric latitude indicia where the map indicium has geographic latitudes corresponding with the concentric latitude indicia on the solar dial. The solar dial also includes a plurality of solar time indicia radiating generally outward from the index point drawn with respect to the noon hour point according to the hour line equation at each concentric latitude indicia intercept. An elongated gnomon projects from the index point, whereby the sun's shadow cast by the gnomon intersects the solar time indicia in relation to the concentric latitude indicia to provide a reading of apparent solar time for the user's location on the map indicium.

Description

FIELD OF THE INVENTION[0001]This invention relates generally to planar sundials and specifically to an apparatus and a method by which a planar sundial can be constructed to tell time, both solar time and clock time, over a range of latitudes and longitudes by means of map indicia integrated with the sundial.DISCUSSION OF PRIOR ART[0002]Sundials can be classified into two broad categories, equiangular sundials and unequiangular sundials. Equiangular sundials are characterized by having their hour lines spaced at equal intervals on the dial, usually a spacing of fifteen degrees agreeing with the fifteen degree revolution of the earth in one hour's time. Sundials of this category are most often constructed using a surface of revolution, examples being a sphere, a cylinder, or a cone, on which surface the gnomon's shadow is cast. The gnomon is commonly fixed at the center of the surface of revolution. Unequiangular sundials are commonly implemented with a dial in the form of a planar s...

AI Technical Summary

Benefits of technology

[0029]a) this apparatus allows the required latitude correction to be made by visual reference to latitude map indicia together with latitude dependent solar time indicia included on the sundial, eliminating a need for understanding lines of latitude, or knowing one's latitude, or of adjustments, tables of correction or mental calculations;

[0065]In an alternative embodiment of the present invention, both the gnomon and the gnomon support are made removable and means for stowing both lying flat on the sundial's surface are provided for easy transport.

Problems solved by technology

However, these non-linear hour lines do not show, either in function or in use, curvilinear solar time indicia.

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