The circle is divided into sixteen equal parts. Rhumb lines connect to the points on the circle and provide a grid.
The rhumb lines on the map could be followed to navigate a vessel at sea; the grid made from them could be used to copy this portolan chart. [For more detailed circles in separate windows, click on the images.]
The five scales of distance could be used to determine distance along the rhumbs.
One compass rose is located in southwestern Africa; a second is found in the northeastern part of the map.
Can you find the compass roses and the scale on the Large 1489 Chart?
| Under the Magnifying Glass
The 1489 Canepa
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