What are these lines called and what are they for?

I saw this map over at the Cartographer's Guild. It has these straight lines over the ocean that go off of the map and some of which point to locations in the ocean. What do the lines represent and what do the spots on the ocean represent?

http://www.cartographersguild.com/attachments/finished-maps/49920d1352984170-thuria-thuria-small.jpg

Comments

Sign In or Register to comment.