Portolan Map Possibilities

[Linda]

The map or chart at a 45 degree idea had me wondering, why would it be presented to be viewed in such ways? For personal reasons, which happen to obfuscate the information from others? I had thought perhaps someone in Italy would have seen maps of the Italian peninsula as up and down, rather than on an angle, and projected that onto the world. But then i thought maybe they may have been sitting at a corner of a large map and just learned to see it that way. Or, as i just came across, perhaps someone had a globe and made it up like a combo of Crates and Oresme.  This is what they'd see, except anything below the equator would be thought to be water, if they held to that line of thinking. But perhaps we catch a glimmer of the next wave of thought, we add Ptolomy back into the mix. By then several people and their stories of China had been documented and more were coming. Ptolemy not only described a map, but things like stereographic projection and how the earth would be best represented as a sphere. His works began to be reintroduced to Italy around 1300, and were being translated from Greek to Latin in 1406, so it is possible that there were earlier versions than the oldest surviving, in fact it is known that some were commissioned, but did not survive. 

The Behaim globe shows the exact ecumene of the vms quire 13 periplus in its upper half. This half would be the one on the right in an Oresme style tripartate inverted TO map.



Although the angle here would be about 23.5 degrees or so, the perspective of a point on a globe shifts in degree if you move the viewpoint. So a person sitting slightly to the right of the globe set in this manner might see it at a steeper angle. It may also explain 90 degree views of things, if the copyist tended to sit on one side or the other.  Or maybe it was not a globe at all. 



With this projection, the portion that is shown on s portolan chart is on an angle also.


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