Assignment 5

Conformal Projections

Equidistant Projections

Equal Area Projections

          The selection of map projection is dependent on how one wants to convey specific information.  All projections fall under three categories: Equal Area, Equidistant, and Conformal.  Each category has different guidelines on how the spatial data is presented.  Equal area projections preserve equivalent areas to their real-world counterparts, while equidistant projections preserve equivalent distances and conformal projections preserve local angles which account for equivalent shapes. 

          Conformal maps preserve shape proportions but lose size proportions in the process.  This is obvious in the Mercator projection where the lines of latitude are increasing in distance as they move further from the equator, distorting Greenland and Antarctica to extreme proportions.  In the Stereographic map, Australia is shown as big as the U.S. and Canada combined. This also distorts space between locations, giving a distance from Washington DC to Kabul much higher than the true measured distance. 

          Equidistant maps preserve distance proportions but lose size and shape proportions in the process.  An equidistant map gives the closest approximation of the distance from Kabul to Washington D.C. to its true distance of 11,153 km.  This map is distinguishable due to the equal distance between its lines of latitude and longitude.  In the Equidistant Cylindrical map, South America is obviously stretched out vertically to preserve distance.

         Equal Area maps preserve area proportions but lose shape and distance proportions in doing so.  The margin of error in terms of distance is usually less then conformal projections but not as good as equidistant projections.