The Greenland Problem And Playing With Mercator's Map
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.
A really effective way to show this distortion in action is the Mercator Puzzle by Luke Mahe of the Google Maps Developer Relations Team. Drag and drop the red shapes, which represent countries, around the map; watch them shrink as you near the Equator and expand and distort as you move towards the poles.
It's a nice geographical puzzle and an equally nice way of showing Mercator in action; how many of the 15 countries did you manage to find their correct homes for? If you're really stuck, there's a solution here; but no peeking unless you really get stuck!
Picture Credits: Mercator Map Wikimedia Commons, CC-BY-SA 3.0.
