What is a projection?
A projection is the operation used to convert between a location (latitude/longitude) on the surface of a sphere (globe) to a location (x/y) on a plane (map). Now, you may ask, what’s so difficult about converting from spherical coordinates to Cartesian coordinates? Well, try this experiment – using an exacto knife, try to cut a ping-pong ball into pieces that lie flat. Can’t be done. Now, also using a knife, cut the peel of an orange into pieces that lie flat. This can be done, sort of, if you are willing to stomp on the pieces until they stretch some. So… you can’t convert between the surface of a sphere and a plane without distortion. Which projection should I use? The short answer is – Whatever projection your existing maps use. The long answer is – Whatever projection your existing maps use. If one is mapping an area that has never been mapped (not likely on this planet), one can choose almost any projection.
A projection is a methodology for converting a portion of the spherical earth surface (ellipsoidal actually) onto a flat surface such as a paper map or Cartesian coordinate system. This is important for visualisation and terrain analysis. There are many types of projections available, they use different approximations of the earth as an ellipsoid (semi-major axis and flattening parameters), different projection methods (such as cylindrical, transverse cylintrical, conic etc) and each of these projection methods can be customised using different projection parameters. No single projections can conserve all map quantities and all will introduce distortion into a map. For example the Mercator projection is used extensively for world maps in which the distortion towards the polar regions grows large which giving the impression that, for example, Greenland is larger than South America. However, in reality, the South America is about eight times the size of Greenland. Some projections consev
