Appendix B. Map Projections
This appendix describes some common and uncommon map projections. Introduced in Projections and Coordinate Systems, map projections are the many different ways of translating the shape of the Earth, which is like sphere, onto a flat surface.
Note
For a much more in-depth look at the many different kinds of projections there are and what benefits and disadvantages they possess, with pictures, Map Thematics has an amazing list of projections.
WGS 84 (Latitude and Longitude)
The World Geodetic System (19)84 projection is a variant of the Mercator projection, but without the assumption that the Earth is a sphere (actually an ellipsoid). This is the projection that GPS systems use. It has the same limitations of the Spherical Mercator that were discussed in Projections and Coordinate Systems. When you get to the local level of detail on a map, you will find slight differences in position from the spherical Mercator.
Note
The WGS 84 projection has the EPSG:4316 identifier.
Gall-Peters Projection
The Gall-Peters projection represents the world in a rectangle, but preserves area. This is a stark difference from a Mercator projection, as it address the Greenland problem (in a Mercator projection, Africa and Greenland look the same size; Greenland is actually around one-tenth the area of Africa). You will not usually find this projection used in web mapping.
Note
The West Wing, an American TV show, has a fun episode where a side storyline involves this projection. The White House press secretary is presented with a Peters world map and is taken aback by the difference in the world view. The video clip and explanation are on the ODT Maps website.
South-Oriented Maps
A south-oriented map puts south at the top of the map and north at the bottom. This is an important (and shocking to some) notion, as the idea of “north on top” is an arbitrary designation. The ubiquity of north-oriented maps is believed to have a significant effect on our view of cultures in the north and south.
Though not a projection, a popular map that has this orientation is the McArthur’s Universal Corrective Map of the World.
You will be very hard pressed to find a web map that is south-oriented, but there is work being done to make this a much easier task. As of recent, there is an official projection code for a Transverse Mercator (South Oriented): EPSG:9808.