The Carta Pisane has been the subject of much speculation since it surfaced in Pisa. Is it the oldest known example of the genre of Portolan Charts, the dating is rather nebulous: was it drawn using the text of “Lo Conpasso De Navegare” (LCN): was it used at sea, thus its deleterious state: why does it appear to exhibit far more than the supposed next set of charts by Pietro Vesconte: is it merely a wishful thinking plot and not reality in the extreme areas of the chart. All of these points have been discussed ad infinitum by researchers, but the actual chart I believe has never been the subject of a forensic cartographical examination until now.
The only definite from the above list that can be quantified concerns “Lo Conpasso De Navegare” and that has been shown to be unlikely as the source of the chart using the “Starea” descriptions alone. This paper concentrates on the technical cartographical aspects of the chart, its scale, draughtsmanship and the methodology that was probably used to construct the basic outlines, but at all times uses the LCN as the basic parameter. Whether that is a correct assumption may be argued, but at least it is a basis for evidential research. The Peleio distances are shown to be the primary source of distance measure for the chart with their wind directional component. It is then shown that the actual coastline between node points gained from the Peleio distances is freehand drawn, mostly guessed, but some with real knowledge of the shape and form of the littoral.
The two wind roses are shown to be dimensioned using the same mathematics as the “Tavola De Marteloio” for the 45 degree alignment, that is 71 units, and thus the overpowering square features located in four positions on the chart are quantified.
There are correspondences and also complete differences to “Lo Conpasso De Navegare”, and thus that text does not provide for an adequate guide to the charts origins. But, the Carta Pisane is a carefully constructed chart suffering from the vagaries of poor and corrupt data producing distortion, not magnetic declination, and neither does it produce a chart usable for Pelagic Sailing because of the distortions there-in.
It is however in part well drawn and requires visual assessment over and above the first impression it unfortunately portrays by its state of preservation.
The text is 16 A4 pages and contains 25 + 2 A4 diagrams.