But they did have Navigation charts and plotted courses. I don't care if it's not exact location, and I believe it shouldn't show any other ships, but they did use Navigational charts of the none world. Which by this time most of this area was pretty well known. Go watch Master and Commander and you will see them using navigation charts to plot there course. They could pretty much pin point there location to real close to where they really was cause of those charts. This isn't the viking area where you had to keep close to shore, these are mostly ships that did go a bit from the coast and crossed the ocean instead of taking the long path along the coast (though safer path).