Map projections are an extremely important aspect of GIS. In order to represent the earth, which is a sphere, in a two-dimensional matter map projections must be used. When trying to display the earth on a two-dimensional plane, deformation is inevitable. Depending on which projection you use, different aspects of the earth will be deformed. Depending on what you want your map to portray there will be a certain projection that will preserve the dimension which will best suit your map. The three projections we used in this lab were equal area, equidistant, and conformal.
Equal area map projections preserve the areas of the earth. This type of projection can be useful when you want to show the actual sizes of landmasses relative to each other. For example, if you were to look at a Mercator map, you would think that Greenland is a very large country relative to other landmasses, when in reality its size is much smaller. When you use an equal area map projection such as sinusoidal or bonne projections you can really see the continents’ actual sizes relative to each.
Equidistant map projections preserve distance from a defined point or line. The Plate Carree map projection preserves distance from the equator. This map projection is appealing because it portrays the earth as a very simple rectangular map. The two point equidistant projection sets two points and the distance to these points from any point on the map is preserved.
Conformal map projections preserve local shapes and angles. These maps are most accurate at a local scale. The stereographic map preserves the shapes of circles. The hotine projection is another conformal projection. These projections would be useful for navigation in a localized sense.
As you can see by looking at the distances measured between Washington D.C. and Kabul they change. Obviously in reality the distance will always be the same, however the fact that these distances were measured on different projections caused them to be different.
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