Is there any explanation for this from him? I haven't found anything.
Here are his maps: http://www.myoldmaps.com/late-medieval-maps-1300/240-albertin-de-virga-world/240-de-virga.pdf
Here are his maps: http://www.myoldmaps.com/late-medieval-maps-1300/240-albertin-de-virga-world/240-de-virga.pdf