So this blog I follow for Aubreyad content also posts a lot of Age of Sail stuff in general, and I saw this meme and understood exactly zero percent of it but figured that meant it just needed to be here
I know it's a joke about map projections, so if my googling is correct, I think the explanation is Spoiler: explaining the joke the top image is a portolan chart, a type of nautical map with networks of rhumb lines, which represent the direction you'll go if you sail towards a particular compass bearing without ever changing course. This makes it easier to figure out which direction you need to point the ship if you're crossing a comparatively small and heavily-traveled body of water like the Mediterranean Sea, but pretty bad for crossing open ocean because they don't account for the curvature of the earth- rhumb lines are actually great big spirals if you draw them on a globe, not straight lines. The second one is a Mercator projection, which turns latitude and longitude into a grid; while this wildly distorts the apparent size of everything the closer you get to the poles (no, Greenland is not 3 times the size of Australia), it lets you measure bearings correctly even across huge stretches of ocean.
