The Wikipedia article linked is actually very complete on the properties of each projection: http://en.wikipedia.org/wiki/List_of_map_projections http://en.wik

The Wikipedia article linked is actually very complete on the properties of each projection: http://en.wikipedia.org/wiki/List_of_map_projections http://en.wikipedia.org/wiki/List_of_map_projections See the "Properties" column and description of each at the end. Mercator is marked as "Conformal", which means local angles are preserved. I believe that basically means if you are going 45°, and you draw a 45° line from your current location on a Mercator map, you will end up where that line goes. Which explains why it's so good for navigation.