Orthographic projection
Topic: Map Projections · NCERT: Class 11, Ch 4 "Map Projections"
Meaning
An orthographic projection is a perspective projection with the light source at infinity, which means very far away. The rays of light therefore reach the globe as parallel lines. The resulting map looks like the globe seen from far out in space. Shapes near the centre look natural, but areas near the edge get squeezed. It is used mainly for pictures of a hemisphere, which is one half of the earth.
Example
A picture of the Eastern Hemisphere centred over India, showing Asia, Africa and Australia as a round disc, is an orthographic view. India looks natural at the centre, while the coasts of Africa and Australia near the rim look squashed.
Don't confuse with
- Orthomorphic projection: this means a "true shape" (conformal) projection, like Mercator. It describes a preserved property, not where the light is placed. The two words sound alike and are often mixed up in exams.