Indeed, the hole point of the projection was to make navigation easier by allowing rhumb lines (the shortest distances between two points on a curved surface) to be charted as perfectly straight lines on a two-dimensional map. From these lines of constant bearing, mariners could work out the precise - and constant - angle they should maintain in relation to the pole star in order to get from one point to another.

Without a reliable method for establishing longitude at sea, 17th Century navigators could never be exactly sure how far along their courses they were, but at least they could know that they were heading in the right direction. Given the level of uncertainty involved in these enterprises, this one piece of (relatively) hard and verifiable data was extraordinarily important, making the accuracy of the projection, and the mathematically - if not visually - correct placement of shorelines within it especially important.

Unfortunately, the iconic value of the Mercator projection has vastly outlived its utility - or at least, the common awareness of the once formidable navigational problems it addressed. Far from seeing it as a brilliant technical solution, it is often seen through a purely political filter that views its strengths as weaknesses, while completely missing the map's actual intent.