From Online Dictionary of Crystallography
Projection stéréographique (Fr). Stereografische Projektion (Ge). Proiezione stereographica (It). ステレオ投影 (Ja). Стереографическая проекция (Ru). Proyección estereográfica (Sp).
The stereographic projection is a projection of points from the surface of a sphere on to its equatorial plane. The importance of the stereographic projection in crystallography derives from the fact that a set of points on the surface of the sphere provides a complete representation of a set of directions in three-dimensional space, the directions being the set of lines from the centre of the sphere to the set of points. The most common application is that of representing the angles between the faces of a crystal, and the symmetry relations between them.