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In 2013 I was sent a response to my informative letter and drawings discussing the Fra Mauro planisphere by Professor Piero Falchetta. The diagrams clearly showed that it had been “constructed” and even outlined the geographical graticule I had determined.

The response was as follows;
Dear Michael, finally I can reply to your letter of last January, that on Fra Mauro’s map. I think that your work, very accurate indeed, doesn’t fit in with Mauro’s work. I would say that his map wasn’t drawn with the support of some kind of geometrical scheme. This is the reason why it is absolutely inadequate to “measure” his map with the mathematical method. Mauro unequivocally refuses the Ptolemaic cartographic method when he writes: “So if someone contests the work because I have not followed Claudius Ptolemy either in the form of the world or in the measurement of latitude and longitude etc.” (note 2834 of my transcription in my 2006 book)
Measuring Fra Mauro’s map and expecting to obtain from this measurement any kind of information on his own method of composition is, in my modest opinion, wasted time.
With best regards, Piero Falchetta

I was very bemused by the response as it was patently obvious a linear scale had been used (Vatican chart) and sought an opinion from a specialist historian, (Doctorate) who helped me to understand Latin quotes and context I found I could not translate. I sent the relevant information and now include the response.

“Thank you for your message. Unfortunately, neither cosmography nor early modern Italian is a specialist area of mine, so I can only give an amateur’s opinion. Falchetta’s translation of 2892 seems to me fine (and far superior to the second translation you quote). Fra Mauro is clearly defending himself for deviating from Ptolemy regarding meridians, parallels and degrees in some parts of the map. It should be easy to demonstrate this: however, it is interesting to note that Mauro does not choose to defend himself by saying he actually uses Ptolemy’s meridians &c, but with only some specific deviations. Rather, he suggests that the need to accommodate lands now better or newly known has had a fundamental effect upon his choice of meridians &c. Clearly, if he uses the Ptolemaic meridians &c elsewhere, these must be in parts of the map not considered important or contentious.
Unfortunately, I do not know enough of cosmography to know whether you can follow just some meridians &c but change others, or whether changing even some has a knock-on effect over the whole map.”

This answer was much attuned to my own summation of the paragraphs 2828 and 2834, pages 699/700, and 2892, and page 711, that I concluded the work should continue at a later date.
What I could not understand was how in the 2006 book page 38, regarding the Borgiana V Portolan chart and reading that it was a forerunner of the Fra Mauro chart, the statement was made that “The linear scale appears on the false neck of the parchment”. Look at that chart, because if a preparatory drawing for the Planisphere had a Scale Bar, then it equally applied to the Planisphere as they are stated as basically one and the same which will be indicated later.
That was the basis of my preliminary works and will now be fully explained in this narrative.

Firstly, the text by Professor Falchetta is both extensive and detailed removing the necessity for constant repetition of it and I have only used it here for a series of notes.

In his introduction Professor Falchetta posed a series of questions (page 19) in paragraph two as follows:
Not only are the questions raised by such a work largely unanswered: they are largely unposed. In the present case, knowledge of the world map would imply asking: what does it show us? What geography is depicted there-in? What knowledge is it based upon? And how was it possible to co-ordinate and correlate such a mass of information? Similarly, one would like to know what relation the world map reveals to contemporary knowledge and science, how far it drew on- or added to-them. And finally, how exactly are we to judge this great undertaking of Fra Mauro’s? Is it the mature fruit of a centuries-old tradition of medieval geography or does it herald the advent of knew geographical knowledge?

He then comments that, “this study aims to provide systematic answers to such questions”, but as this text is predicated upon the fact that “it was not drawn with the support of some kind of geometrical scheme”, I could not understand why a graticule of latitude and longitude, a geometrical scheme, which Claudius Ptolemy stated should be a 5:4 ratio at 36N, the centre line of the Mediterranean Sea, would be so dismissed when it can clearly be shown to be the basis of the Vatican Chart and Fra Mauro’s planisphere, as my preliminary work clearly indicated.

Then from page 33, “Sources, Evidence and Models”, he commences as follows;
“As the author himself informs us in various inscriptions within the world map, the work involved painstaking and long preparations. However, not one of those preparatory notes or partial drawings have come down to us; nor do we have any contemporary record that enables us to understand the “method” followed by Fra Mauro in creating a work that, when compared to the cartography of the day, strikes us as innovative in a number of ways. This means that if we are to trace the source, tradition, idea or commonly –held belief behind the individual (cartographical and textual) components in the map, the work must be ‘dismantled’- a procedure which will not only give us a better understanding of the map’s contents but also enable us to place it more accurately within the context of contemporary cartography”.

He continues in paragraph three (first 5 lines)
“In effect, the sources, evidence and models used in the creation of the map fall into three categories: there are cartographical documents ( mappamundi, regional maps, nautical maps, etc.), written texts (for example Marco Polo, Nicolo de Conti, etc.) and the no longer identifiable oral accounts which, as Fra Mauro himself comments, were very important in the creation of the finished work”.

and concludes paragraph three as follows;
“the complexity probably meant the work was carried out in stages, with the creation of partial maps, similar to the Borgia map prototype, which would then be transferred to the complete map using the copying and tracing techniques that were common at the time57. (Falchetta, 1995, pp70-75. The idea that Fra Mauro constructed his world map through the juxtaposition of partial maps finds support in a couple of inscriptions- for example #98, in which he says, “tuto questo desegno da sayto in suso io l’o habuto da queli proprij che sono nasudi qui”. And certain errors- foremost amongst them those in the drawing of the Indus and Ganges-seem more likely to have been the result of unsuccessful assembly than of imperfect geographical knowledge”).

Here we read definitively that partial maps similar to the Borgiana V Portolan chart were used. Thus on page 36 commences a brief description of that map although a full comparison of the numerous texts there-on is made. Professor Falchetta commences;
The starting point for any discussion of the sources used in the world map must be the Borgiana V, a map now in the Vatican Library. As one will see below, I would argue that this is a copy of one of the preparatory drawings that Fra Mauro used in creating his work; hence, it is necessarily earlier than the world map and, in a certain sense, one of the sources. However, given that the relation between the two maps is not entirely clear, the whole matter should be re-examined in some detail.

Then both Professor Falchetta and H Winter (text, The Fra Mauro portolan chart in the Vatican) state the Borgiana V Chart is 132.5 x 75 cms and is made up of three sheets of parchment of unequal width.
I will refrain from commenting here other than to say this is totally awry and I deal with this Portolan chart in detail as a separate item later.

I conclude this cursory examination of the 2006 text from this section with the last four lines from paragraph one, page 48;
What is more, the reference to Shah Rukh makes it possible to date CB in the last years of the 1440’s, when the immense task of collecting and collating the data and information for the drawing –up of the world map can be said to have been fairly advanced, if not entirely completed.

And, from the final paragraph page 52 of this section as follows;
In conclusion, therefore, there would appear to be support for the following points, 1) CB is almost certainly the copy of the lost original; 2) CB is certainly unfinished; 3) the original was a sort of dress rehearsal for the world map; 4) Fra Mauro drew up various regional cartographical maps; 5) It is possible that CB itself may be seen in relation to the copy made by the Florentine painters some time before 1480; 6) In moving from CB to M, Fra Mauro had access to new sources, or put those he already had to different use.

The following sections in the book are; Ptolemy and other Cartographical models; Marc polo and other authors; The Oceans; Asia and Russia; Africa; N Europe and the Atlantic Islands and cosmological notes in the four corners are explained.
However, on page 141 he discusses Fra Mauro himself and on page 143, “The dating of the world map” and commences with; “As the extensive arguments put forward in this volume suggest, the world map was probably drawn up around 1450. However, these arguments cannot link the drawing of the actual map to a specific year, as the completion of that work will have required some time after the compilation of the contents.” And then, “All of this, therefore, would argue in favour of dating the Marciana work at around 1448, and definitely prior to 1453.
Following a short further section the book then provides a complete listing of every place, title and text that appears on the planisphere, 2921 in total.


This section is actually out of date order but provides more information with which to judge the following as the 1436 atlas page indicates.
In a previous text reference Ch WAF/1, I fully examine the 1448 chart and thus utilise diagrams there-from which provide the basis for a comparative study with the Borgiana V Portolan Chart and the Fra Mauro planisphere.

However, before commencing on the 1448 chart comparisons it is necessary to discuss the fifth sheet in his 1436 Atlante Nautico as the false neck of the Borgiana V chart includes the linear scale and it appears to be similar to this sheet. It would be wrong to think that Andreas Bianco would not have a draft copy or pattern/template for his Atlante Nautico as well as the corresponding data for the 1448 chart with him when he arrived at San Michele, Murano.


The atlas page provides for an excellent western extent of the Borgiana V Portolan chart, fitting well into the neck of the parchment. But why should it be considered a false neck to the Borgiana V Portolan Chart, when the cartographer is obviously endeavouring to produce a Portolan Chart, scaled to Miliaria and being of a standard format used for c150 years.

The 1448 chart diagrams ChFM/1/D02 to ChFM/1/D05 illustrate the latitude/longitude and toponyms for the West African coast from Cape Spartel to Cape Verde/Cape Rosso.





A second diagram ChFM/1/D06 is included which sets down the toponyms on the Borgiana Chart, the 1448 chart and the Geographical equivalents set down on the 1448 profile. These were somewhat harder than normal to read and evaluate and with the assistance of a Palaeographer I include our attempts on the diagram.


Thus it is possible to meld the 1448 chart and the Borgiana chart to illustrate any similarities and this is exhibited on two diagrams ChFM/1/D07 and ChFM/1/D08.

ChFM/1/D07 & ChFM/1/D08


In 1962, Heinrich Winter wrote in “Imago Mundi” a monograph entitled, “The Fra Mauro portolan Chart in the Vatican”. He comments that Robert Almagia established this chart is not the work of Fra Mauro himself, but the work of a copyist after an original by Fra Mauro, which must be dated prior to the World chart.

Winter makes three points which can be given in précis form as follows;
1) the tapered neck is not therefore natural in origin, but arbitrary, although it involves sacrificing part of the important West coast of Africa.

To which I comment; study the neck and note that the scale bar is the charts defining western boundary with the wind rose lines finishing there. Then look at the western section, the junction between the second and third sheets and again the wind rose lines stop at that junction. But there is no comment in the text or any text I have seen which notes those two features. It indicates that the third section, the eastern section is a later addition to the main Portolan Chart and was probably included to ensure maximum coverage of the data that was being analysed by Fra Mauro. It includes Delhi in the south and Samarkand in the north and has been so designed to provide adequate space for nailing it to a rod as can clearly be seen

The second point is completely nonsensical; “so that we cannot speak of a definite orientation of such charts, compass roses and signs indicating north are not conclusive in this respect, “a proper portolan chart”.



The wind rose graticule is always set out geographically NSEW and has a precise construction whether drawn with or without a circle as my texts ChWr/1 and ChWR/2 clearly illustrate as does Petrus Vesconte in his 1318 Atlas.

The third point, “Like the world map, the Vatican chart is a chorographic map”. That is “pertaining to chorography; descriptive of particular regions or countries; laying down or marking the bounds of particular countries”. Thus hardly any Portolan Chart or map is not chorographic!

H Winter then reproduces all 40 texts, translated by a specialist in 15th C Italian.
But this Portolan Chart is far more than both Winter and Falchetta require it to be, a historical descriptive parchment, which is their main analysis of the Borgiana V chart. A Portolan Chart is in fact a technical construct based upon latitudes and longitudes and distance measures which are generally set down to the Ptolemaic proportion of 5:4 at 36N. They practically all have a scale bar which can be used to determine the distances and those that do not have one, by studying the west coast of Iberia, that is from 37N to 43N the scale can be found.

If you study my texts it will become patently obvious that the Portolan Chart is a constant continuous construct which hardly develops over the two centuries of their existence, 1300’s to 1500’s. The West Coast of Iberia is always drawn at 75 units per degree and thus the scale bars on most charts are Miliaria of 1.2326KM or 6.666 stades. Thus generally the main chart is drawn to 90 Miliaria per degree being the equivalent of 75 Roman Miles or 600 stades. The West coast of Iberia is drawn wrongly as the original chart cartographer mistook the Roman Mile measurement for Miliaria. Given those facts and the wind rose setting out of 35/30/20/7 ratio units per quadrant for the graticule any chart can be evaluated for measures.



The Borgiana V Portolan Chart can be shown to exhibit all of the above features for the normal extent of a portolan chart, generally 18W, the Canary Isles to 42E, the eastern Black Sea as diagrams ChFM/1/D11 and D12 illustrate. From there the addition of the Caspian Sea in a geometrical form, but tilted some 60 degrees anti clockwise, then Samarkand at 39 40N, 67 00E and Delhi, 28 38N, 77 17E, indicates a chart stretching from 20W to 80E geographically. The latitudinal bearings vary from, in the West, 20N to 58N and in the East 20N to 40N with a large void between 33N and 36N encompassing Persia, Afghanistan and the Far East. This chart is set out in a clear geometrical fashion as the measurements show.

The cartographer, and if it is a copy of Fra Mauro’s original, Fra Mauro himself commenced with a standard Portolan Chart format which has an anti clockwise slew and to accommodate the area mentioned above has just continued the slew in the north and then introduced a slew clockwise in the south forming a large void into which he has drawn the new countries and their format gained from the verbal or textual data he had amassed, but always guided by the original works of Marinus of Tyre and Claudius Ptolemy.

The simplest of all methods and one William of Oakham would have been proud of!

Returning to the size of the Borgiana V chart as presented today, which if it was a vellum skin some 132.5cms long would in all probability be at least 90cms in width (N/S). The junction of the second and third pieces is worrying in that the roads do not align and this perhaps indicates that originally the chart was only a small section longer in the east, perhaps nailed to a rod and has been cut and joined, not very successfully to the third section extant. That in my mind raises the spectre of a second portolan chart and they have been cobbled together? The N/S reduction could therefore be because the second portolan chart was in fact not as wide as this chart was originally and the reduction is to align both to provide a matching width, Thus we have an extant chart some 154cms long and 75cms wide.


The Borgiana V Portolan chart has been overlaid to the Fra Mauro planisphere. The result indicates that there has been a gradual lengthening of the distances from the 36E longitude to the 18W longitude of the Canary Isles although they are similarly positioned. The expansion is capable of being aligned section by section in the Mediterranean Sea basin and is thus a draughting change which has some ramifications for the Fra Mauro chart. That change in the Fra Mauro chart can be attributed to the use of the 75 units per degree of latitude as will be shown later.






The basic Andreas Bianco profile for the West coast of Europe and Africa to 28N has an acceptable similarity except for the British Isles. The major difference is the West coast of Africa from 28N southwards to Cape Verde at 15N. But given the putative dates for Fra Mauro, Andreas Bianco is more likely to have drawn the chart in London to a standard portolan chart, hence some agreement. But, Andreas Bianco’s work may well have been more to do with the following planisphere bound for Portugal with amendments noted there-on.


Drawn on three A3 sheets which all overlay join to form the whole planisphere, the latitudes and longitudes, which are entirely geographical are appended using the Borgiana V Portolan Chart scale bar for distance measures, which are Miliaria. The outline of Borgiana has been indicated to illustrate the extent to which it actually controls the whole planisphere.

But it is obvious that Fra Mauro has decided that the base unit for his chart is 75SBU’s per degree probably thinking that emulates the Roman measure and thus produces a SQUARE CHART with latitudes and longitudes agreeing. This confirms the change shown by the overlaid Borgiana chart with the Fra Mauro chart where the distance measures varied.

From the complete layout it is possible to see the anticlockwise slew along the Mediterranean Sea being continued by Fra Mauro, exaggerated north and south to provide the central area on which to draw Asia, India and China.


ChFM/1/D18 & ChFM/1/D19

But it should be clearly noted that by continuing the 36N centre line of the Mediterranean Sea that it clearly indicates the Imaus Mountains which Claudius Ptolemy states are at 36N. Thus the splitting of the geography from 33N to 36N has allowed the areas of Asia, India and China to be accommodated but to provide for a central pivot to the planisphere for these areas the Imaus Mountains are “correctly” positioned geographically. Therefore it is obvious that Claudius Ptolemy played a greater part in the overall layout than Fra Mauro cares to admit.



Given that the entourage on Murano working on the Planisphere were using data gathered prior to c1445, a curious situation arises. We are informed that Fra Mauro passed away c1459 and probably oversaw the preparation of the copy Planisphere destined for Portugal

What we are discussing is as follows, shown on Diagrams ChFM/1/D21 and D22.



Andreas Bianco produced his Atlas in 1436 but the Atlantic Coast chart is dated 1448. Hence in all probability he was not in Venice until 1450 at the earliest.

The Planisphere of Fra Mauro was drawn c1450 with a spread of dates given as 1448-1453.

But on the Planisphere we read Note 561 given as; Nota che dal cavo verde in suso non se vede la tramontana, translated as Note that from Cape Verde south one cannot sea(sic) the Pole Star.

Firstly I had great difficulty translating that actual text written upon the planisphere as follows; Nota che dal cavo verde ifufo nofe vede latmo tana with ticks over the letters o and a squiggle over latmo as the photos appended to the diagram indicate.

We know that Cape Verde was discovered c1444 by the Portuguese, but how much further south then is not known, possibly even to the River Gambia. That area was certainly explored by Alvise da Ca da Mosto and Antoniotto Usodimare in 1455 and 1456 after the planisphere was drawn. But the planisphere clearly shows Cape Verde (14 42N, 17 27W) and then Cape Rosso which in fact would be Cape Rouge (14 38N, 17 11W) an ill defined point of Reddish Colour. Cape Rosso (Roxo) is further south at 12 20N, 16 43W and at the estuary of the Rio Cacheu, deriving its name from some red patches lying close north of it. Therefore the three rivers commencing north of Cape Verde would indicate knowledge of the Senegal/Gambia River’s which had other mouths than today’s estuaries.

But as stated this area was not explored until 1455-1456 and thus the note regarding the Pole Star must be a later addition and that is probably the same changes as we see on the coast of West Africa as the photo indicates.

The reference to the Pole Star is from Alvise da ca da Mosto, but the attribution of Tramontana to the Pole Star is from the 13th century. The information is as follows;

The reading given by Piero Falchetta seems correct; “nota che dal cavo verde in suso non se vede la tramontana”. SUSO, is an archaic form for SU, that is UP, I believe in the meaning “continuing on the same way”, in this case South.

Alvise da Ca da Mosto says; “Nelli giorni che noi stemmo sopra la bocca di questo fiume (Rio Gambia?) non vedemmo piu che una volat la tramontana (the pole star) e ne pareva molto bassa sopra il mare…..

Antoniotto Usodimare at the end of his navigation; “… si navigassem adhuc diem unum amisissem tramontanam”

This explanation is from an experienced professor;
Fra Mauro; “Upside Cape Verde you can see Tramontana”

P Falchetta; “Downside Cape Verde you cannot see the Pole Star”

Tramontana a wind but in the 13th century it could mean in extension Pole Star.
You can find this meaning in Dante Alighieri and in “The Roman de la Rose”

Alvise da Ca Da Mosto and Antoniotto Usodimare voyaged twice in 1455 and 1456 and the near disappearance of the Pole Star at perhaps the mouth of the River Gambia, 13 28N, 16 40W is strange indeed. The Pole star is in fact visible to the Equator as its apparent height in the sky is equal to the latitude of the observer. Thus it should have been c13 degrees elevation, but even allowing for the 4 degrees of rotation it would still have been at 9 degrees elevation. Thus the possibility that he was further south cannot be dismissed, but in all probability it is poor reading of the sextant to fix the Pole Star. However, this text was not available until “Navigazioni” was written and his visit to Venice was in February 1463, thus it is open to assume that these alterations, the addition of the text etc., were carried out from 1461/1463. There are two sheets indicating in “Red” all the alterations and amendments to the planisphere that are obvious and I conclude that updates were undertaken as and when new data arrived by the assistants who aided Fra Mauro. The two photos are appended to one sheet and indicate text 561, Cape Rosso and Cape Verde including the additional land to the north. Also not that the word Oceanus on many occasions is amended from OCCEANUS to CCEANUS with the first C partly amended to form an O. Unfortunately without the ability to study the Planisphere in depth I am uncertain if the area containing text 561 and the Capes has been amended as the other area is.


The planisphere has been drawn with a definite measurement system at its heart, given that the linear scale bar on the Borgiana V Portolan Chart transfers so easily to the planisphere. Thus travel distances used originally by Herodotus, the Bematists of Alexander the Great, the Romans and then the cartographers Marinus of Tyre and Claudius Ptolemy as well as those quoted in the text Fra Mauro has used have been translated into distance measures and then of course Latitude and longitude, an occurrence even in the Catalan Atlas of 1375. Hence, a geographical construct can be applied to the planisphere and the method of its production determined as this text indicates.

It does not remove the “Awe and Wonder” which it purveys to its viewers but merely explains the painstaking work of Fra Mauro and his assistants in producing many sectional charts to enable the whole to be drawn. The fact that they were all probably based upon the Portolan Chart format should provide for adequate proof of its provenance.

Michael J Ferrar January 2022.