The term ‘rhumb lines’ used in context with old maps, refers to lines of direction extending from the points of the compass. They were an aid to navigation added to maps during the age of exploration. The most common use of rhumb lines was on sea charts. They indicated to the navigator the direction between locations. By placing several roses on a map and extending rhumb lines from them, a pattern of intersecting lines was set up which enabled the navigator to make a visual estimate of bearing to any point on the map from nearly any other point. Rhumb lines bore no relationship to the construction of the map itself but were added after the drawing of the chart.