Gnomonic projection

Projection gnomonique (Fr). Gnomonische Projektion (Ge). Proyección gnomònica (Sp). Proiezione gnomonica (It). номоническая проекция (Ru). 心射方位図法 (Ja).

The gnomonic projection is a projection for displaying the poles of a crystal in which the poles are projected radially from the centre of a reference sphere onto a plane tangent to the sphere. Of all the methods of projecting a sphere, it is the only one in which all great circles of a sphere are represented on a plane by straight lines. It leads however to considerable distortions and does not contain poles of faces with orientation perpendicular to the plane of projection, which instead occur on the primitive circle of the stereographic projection.