It seems that writing about map projections is a little bit like waiting for one of London's iconic red buses; you write one and immediately another one comes along. As I mentioned in my last post, rightly or wrongly, the most commonly used map projection is the Mercator projection. It's not without it's problems or detractors.

A Mercator map gets more distorted the further north or south of the Equator you move. This is often referred to as The Greenland Problem. Greenland has an area of roughly 0.8 million square miles. Africa on the other hand has an area of roughly 11.6 million square miles. So on the map Africa should be roughly ten times the size of Greenland. Right?

But on a Mercator map it doesn't appear so; both Greenland and Africa look to be approximately the same size; and don't even get me started on how Antarctica is now smeared across the bottom of the map.

Whenever you look at a map, be it on the web, on your mobile or on your wall there's a compromise. The compromise is the map's projection. Or to put it another way, the way in which the roughly spherical lump of rock we live on can be unwrapped and displayed in a flat, two dimensional manner.

There's lots of way of doing this and the ways come with wonderful, almost eccentric sounding names. There's the pseudo-cylindrical projections; Sanson-Flamsteed, Luximuthal or Kavrayskiy's Fifth Projection (no idea what happened to the first four). There's the conic projections; Lambert's Conformal or War Office Polyconic. There's the pseudo-conic projections; Stabius-Werner and Bonne. Or there's the modified azimuthal projections; Wiechel's or Winkel's Tripel Projection.

There's just so many ways of projecting the Earth onto a map. But there's also the one we're all familiar with. It's Gerardus Mercator's Projection and we've been using it, probably without knowing it, since 1569 and it's showing no sign of going away.