thumb|upright=1.25|Orthographic projection (equatorial aspect) of eastern hemisphere 30W–150E
upright=1.25|thumb|The orthographic projection with [[Tissot's indicatrix of deformation.]]
Orthographic projection in cartography has been used since antiquity. Like the stereographic projection and gnomonic projection, orthographic projection is a perspective projection in which the sphere is projected onto a tangent plane or secant plane. The point of perspective for the orthographic projection is at infinite distance. It depicts a hemisphere of the globe as it appears from outer space, where the horizon is a great circle. The shapes and areas are distorted, particularly near the edges.
History
The orthographic projection has been known since antiquity, with its cartographic uses being well documented. Hipparchus used the projection in the 2nd century BC to determine the places of star-rise and star-set. In about 14 BC, Roman engineer Marcus Vitruvius Pollio used the projection to construct sundials and to compute sun positions.
Orthographic projections onto cylinders
In a wide sense, all projections with the point of perspective at infinity (and therefore parallel projecting lines) are considered as orthographic, regardless of the surface onto which they are projected. Such projections distort angles and areas close to the poles.
An example of an orthographic projection onto a cylinder is the Lambert cylindrical equal-area projection.
See also
- List of map projections
- Stereographic projection in cartography
References
External links
- Orthographic Projection—from MathWorld