The Projection reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Projection

The word projection can mean more than one thing.

• In cartography, a map projection
• In psychology, psychological projection
• 3D projection, orthographic projection and isometric projection are ways of representing 3D scenes in 2D; see graphical projection.
• In mathematics a projection is a linear transformation which remains unchanged if applied twice (p(u) = p(p(u))) (in other words, it is idempotent), such as that taking (x, y, z) in three dimensions to (x, y, 0) in the plane or generalisations of this in other dimensions. See orthogonal projection, projection (linear algebra), projection operator.
• In cinematography, projection is the display of a movie in a theater using a film projector, which is likely to be replaced by digital projection

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