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Map projections

Map projections are 'designed to depict with reasonable accuracy the spherical earth in two-dimensional media' (DeMers 1997)

There are many different types of projections but there are three main ways of projecting an ellipsoid onto a plane surface. These are cylindrical, conical and azimuthal projections.

The projection of an ellipsoid surface is done using mathematic principles of geometry and trigonometry. The best projection to use depends on the location on the Earth's surface that is being projected.

Each projection imposes its own type and amount of distortion on a map.

The most widely used general projection is the Universal Transerve Mercator (UTM). This is a world standard used for topographic mapping.

Read
http://www.geog.ubc.ca/courses/klink/gis.notes/ncgia/u27.html#UNIT27
for further information on projections.

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