Many old maps have lines like below. Is there a term for a map with that type of lines?
(from http://r-russell0912-dc2.blogspot.com/2011/01/pirate-maps-and-old-maps.html)
My best hypothesis is that the lines may be related to Rhumb lines and therefore Mercator projections.

cartographyandhistorytag. There are lots of good cartographers there. – Jay Aug 13 '12 at 9:56