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gnomonic projection[nō′män·ik prə′jek·shən]
central projection, a map projection obtained by projecting the points of a sphere from its center to a tangent plane. The method was proposed by Thales of Miletus in the sixth century B.C. Of all the methods of projecting a sphere, only the gnomonic projection possesses the characteristic that all great circles of a sphere are represented on a plane by straight lines. In view of the considerable distortions in gnomonic projections, they are used chiefly for representing small sections of a sphere (in astronomy and navigation).