I am confused by my new map of the Westfjords of Iceland. The geographic coordinate grid is rotated slightly, but the map indicates that true north is still the top of the page.
What's going on? I would have thought a flat map would be unraveled so that all the lines of longitude were vertical and therefore parallel to true north.
Importantly, how do I take a bearing on this map? Do I rotate my housing so that it is aligned with the true north arrow or the grid?
Just to be clear, the above photograph contains the entire legend of the map. There is no mention of magnetic declination, which is roughly 15° W in this part of Iceland in 2017 according to this site. Furthermore, the difference between the grid and the north arrow is not 15°. It would be highly unusual for the north arrow to be magnetic and not true north, but I suppose that's possible. I think I understand how to calculate a route given true north and magnetic declination on a map, but I'm not sure how to interpret this map so that I can start planning my route.
In the comments, @imsodin asked if the angles of the longitudinal lines changed on the map. Using a high resolution scan of the map and Illustrator, I think I can conclude that they do very slightly: