Perhaps if he had considered the correct circumference of the earth he would have never set sail (Columbus also made several calculation errors of his own).Other developments in cartography came from the Chinese, the Arabic world during their golden age, the Mongols and from India.Enter Gerardus Mercator, a mathematician, philosopher and globe-maker from Flanders (modern-day Belgium).The Mercator Projection To really grasp the issues with a 2D projection of the world, one must understand the difference between parallels and meridians.But making meridians parallel is not enough to fix the bearing problem.Mercator also proportionally increased the distance between parallels the further away they were from the equator. The big map in your high school classroom, the atlas you’ve used to navigate during a road trip and even google maps are all lying to you.
He also introduced a co-ordinate system to fix geographical features to specific points.
Parallels, as their name implies, are lines parallel to each other, dividing the world from south to north in flat layers, like the layers of a cake.
Meridians divide the world from east to west but, and this is the key difference, they all pass through the geographical poles and are all the same length.
They divide the world not in layers, but like the wedges of an orange.
Which means that in Ptolemy’s projection they appear like curved lines. Ships are very easy to sail by maintaining a constant bearing: a constant angle to each meridian.