King of Seas

I believe that if you look closely the map is just a 7 x 7 Square Grid. (= 49 tiles) Each
overpainted with some island interfaceable graphic.

So you have to find a Cartograph tower inside each one of them - except the ones
marked at the start, and purchase a map from each.

This will slowly fill out your map and the achievement will pop. The square due NE
of center might not have one - i'm not sure, but I got it anyway, so I hope you will too.

/ CM /