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.

• Cylindrical projections are best for locations within the tropics.
  
  
• Conical projections are best for locations in temperate latitudes.
  
  
• Azimuthal projections are best for polar areas. (Burrough and McDonnell, 1998)
  

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.

http://www.geog.ubc.ca/courses/klink /gis.notes/ncgia/u27.html#UNIT27 This will provide background reading on the raster versus vector debate. Feel like trying the questions? Go ahead.