Many old maps have lines like below. Is there a term for a map with that type of lines?
![enter image description here](https://i.stack.imgur.com/NqfHP.jpg)
![enter image description here](https://i.stack.imgur.com/TQ6wN.jpg)
(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](http://en.wikipedia.org/wiki/Rhumb_line) and therefore Mercator projections.

[Beautiful Example](http://www.lunacommons.org/luna/servlet/detail/JCB~1~1~34~90004:By-the-discouerie-of-Sr-Francis-Dra).