Now comprising 10 sheets; the ‘Raxon de Marteloio’, ‘seven charts’, a ‘circular World map’ and a ‘Ptolemaic world map’, they have now been removed from a binding which stitched through their centre fold and presented in a boxed edition folio. It was produced in 1993 as a special publication of 1500 exemplars, (this authors is number 1148), and has a text by Professor Piero Falchetta of the Biblioteca Marciana,Venice, which holds the ‘Atlante Nautico’ and he describes the content (in Italian) but does not attempt to analyze the diagrams or charts cartographically. It is a historian’s narrow view of the ‘Atlante Nautico’.

This paper delves into the construction and draughtsmanship required for the charts, their geometry and trigonometry as well as explaining the ‘Raxon de Marteloio’ principles as set down by Andreas Biancho which have hitherto been basically mis-represented and not forensically examined to exhibit the simple facts. There is also a discussion apropos the supposed Ptolemaic map of possibly indifferent authorship and the problems there-of.

14 A4 pages and 29 full colour diagram maps

February 2014
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The charts within ‘Atlante Nautico, 1436 ’, are all drawn upon the same size parchment, 260 x 380mm, which in all probability was produced as sheets measuring 262 x 393mm, 1 x 1 ½ Palmo and hence the measurement system of the charts can be assessed. The wind rose is constant upon each chart at 240mm which is thus 11 uncia, (the 262mm is 12 uncia, 1 Palmo). However the chart scales differ, but, they can all be shown to be drawn by the same hand, that of Andreas Biancho. However the last sheet, the Ptolemaic World map, although included in ‘Atlante Nautico’ may not be by Andreas Biancho, and thus its very individual form, its non-alignment to other similar maps is questioned.

9 A4 pages and 11 full colour diagram maps

February 2014
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PORTOLAN CHARTS: CONSTRUCTION AND COPYING [Occam’s Razor Methodology (Lex parsimoniae)]

The subject of the Portolan chart is fraught with difficulty, particularly how were they constructed. This text is the description of a forensic examination of the Jorge de Aguiar Portolan (1492) by redrawing, line by line, from basic principles. Used here-in are also many texts to illustrate preceding research. The conclusion is that they were very simply drawn using a graticule, not generally a circle, and a template or pattern was utilized to draw the map itself.

Note, this paper in a basic form was sent for referee’s comments which are included here-in.

Key words: Geographical map; Magnetic basis; Graticule; Template; Utilization of Chart; Portolan or Portolano Chart.

16 A4 pages and 11 full colour diagram maps

February 2014
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The portolan’s of Angelino Dulcert and Jorge de Aguiar are again examined but this time to establish the minutiae of the maps draughtsmanship, as opposed to the preceding text, “Portolan Charts; Construction and Copying”, [ref. ChPo/1] which examined how the whole Portolan could have been drawn. The method of examination chosen is by a redrawing exercise as opposed to a cartometric programme. A paucity of node points and the tendency to produce curved lines which are not part of the Portolan repertoire are the basic reason for the non utilisation. This paucity leaves large areas of sea and tracts of land behind the littoral subject to an averaging of the distortion grids and a tendency therefore to perceive the plot as correct, when in fact it is not.

Thus from an initial visual appraisal of the map to a detailed point by point recognition of the maps form, how they were first conceived and then drawn, the process becomes apparent.

13 A4 pages and 14 full colour diagram maps

February 2014
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Although research into the Portolan Chart genre has been extensive, it appears not one researcher has actually tried to draw a Portolan Chart from first principles. This fact is bemoaned by many persons who consider themselves expert in the field, have written extensively about these charts, but have never drawn a chart or tried to copy one. It is therefore pertinent to ask if the research is all it should be. Why has it not happened?

This text follows the process of a chart from its very basis, the vellum or parchment upon which it is drawn, to the draughtsmanship of the chart and finally how it could be successfully copied without the process being visible upon either the master copy or the second copy. Many texts are used in the analysis and found to be wanting.

22 A4 pages and 17 full colour diagram maps

August 2014
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The text by R J Pujades i Bataller referring to the winds and technical items within Les Cartes Portolanes is contained within pages 473-481 and 513-514. Here-in R J Pujades sets down his research and reasoning for the origination of the physical work entailed in producing a Portolan chart, the process of copying and the possible scales used as a reason for the charts observed sizes. He clearly focuses upon the wind diagrams and its draughtsmanship, but, it can be clearly shown that his reasoning is based upon a false premise. The background graticule can be shown to be the arbiter of the Portolan chart with the copying method to obtain a number of similar charts merely the use of templates. The background graticule assists in the primary positioning of the map, and certainly provides the chart scale.

20 A4 pages and 20 full colour diagram maps

November 2014
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FOUR MARTELOIO SAILING DIRECTIONS 1295/1436AD; Ramon Lull; Michael of Rhodes; Andreas Biancho & ????

When the Portolan chart was developed in the 13th century, it was covered by a myriad of lines to represent wind directions. These were to assist mariners to gauge the sailing direction from port to destination and also correct their course when adverse winds affected the sailing direction. However, as it was then mainly coastal sailing and not open sea crossings the usefulness of the myriad of lines is questioned .
But, distances sailed could be taken from a chart, (the scales were so very small and thus inaccurate), or read from the more accurate Portolano, a list of ports, inter-distances and obstacles to be avoided. As the distances became greater and more routes were across open seas, not coasting, accuracy in the direction sailed and distances covered became necessary. The magnetic compass was one tool giving direction, but its accuracy was poor and possibly not understood, and distance had to be measured by empirical means; inaccurate!
Hence it became necessary to record actual distances sailed such that when adverse winds affected the course, distances off course and then the return course and distance could be calculated. The return course was generally a logical extrapolation from the wind rose; that is if the ship was blown one quarter wind south of the intended course, the return course would be one quarter wind to the north with equal sailing distances involved. But if the off course sailing was the resultant of many tacks it was necessary to know how far had you sailed, how far off course you were and how far you must sail on a return course to find your original course, and that required calculating; an arduous task with doubtful accuracy.
Thus the Marteloio was developed and improved perhaps by usage. What usage it had is unquantifiable as it does not appear in the texts or notes of many mariners. And we must also note that most sailing was done along shorelines not across open sea for hundreds of miles as the Marteloio accommodates. Thus a degree of scepticism is required of Marteloio.
There are four sections to the text covering differing Marteloio papers with new diagrams.

38 A4 pages and 16 full colour diagram maps

Novmber 2014
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The 1403AD Portolan Chart of Francesco Beccari has been studied in a historical and a technical paper. Commented upon as unique for its latitudinal scale and what may be considered a rather self serving, apologetic text for past chart failures, it requires researching.
Ignoring the previous texts for the main analysis of the 1403AD chart, the actual evidence paints a different picture. Thus it is then possible to show by comparison to those texts the technical detail that should have been assessed and thus a more correct conclusion arrived at.
Finally, the 1435AD Portolan Chart of Battista Beccari is also analysed with the obvious necessity of a comparison to the 1403AD Portolan Chart.

12 A4 pages and 20 full colour diagram maps

February 2015
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Within the pages of Les Cartes Portolanes, R J Pujades argues that the background graticule of the Portolan charts, although drawn on each chart, is not ipso facto part of the construction. On page 513/514 entitled “The Keys to success; the wind network and the decimal based scale”, he concludes,

“Does this mean that the wind network played no role in the actual construction of the first graphic designs reproduced in nautical charts? I do not believe so, since it is one thing to deny the usefulness of the wind network as a basic pattern for obtaining new copies from a previously established model, but quite another to extend this conclusion to the initial moments of the configuration of the first models”.

This is shown to be based upon a false premise, from non-researched extant data which is adequately shown upon the Portolan Charts themselves as this text will indicate.

12 A4 pages and 14 full colour diagram maps

March 2015
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Simplicity: Drawing a Wind Rose Graticule Utilize just one measurement and straight lines

The wind rose graticule has been shown to be a simple geometric construct based upon the side length ratios of a triangle for angular deviation. The ratio of the squares when drawn is 35: 30: 20: 7 TRU’s (trignometrical ratio units). But what if the charts size and chosen scale does not allow for an easy conversion of the ratio numbers to scale measures? This text is an appendix for the original ChWr/1; Wind Rose Construction text.

March 2015
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The earliest Portolan Charts numbered C1 to C4 in “Les Cartes Portolanes” and the Lucca Chart are compared to each other and a Geographical Mercator chart. Thus the similarities of draughtsmanship can be observed and as only one set of Portolan Charts by P Vesconte (C3+Atlas) are signed the opportunity of possibly attributing anonymous charts becomes viable as the outlines coincide, in one instance spectacularly.

9 A4 pages and 26 (33)full colour diagram maps

May 2015
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The conclusion to my text ChCs/1 is that the Riccardiana ms 3827 chart was in all probability an original Pietro Vesconte Chart and dated from 1300/1310AD. Via my draughtsmanship/cartographical evaluation it was shown to be the template for the later charts and atlas of Pietro Vesconte. Now continuing the comparative study with five more charts as noted below, the Riccardiana ms 3827 chart would appear to be the template, or its copy or predecessor, the template for other known and unattributed charts of the period. There are minor deviations in the construction of charts discussed and perhaps following this evaluation a re-ordering of some in the L.C.P. sequencing may be found necessary.

There are 7 A4 text pages and 18 (32) A4 diagrams

June 2015
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The atelier of Cresques Abraham (1325-1387) was undoubtedly a continuation of the atelier of Angelino Dulceto (!name!), who probably arrived in Majorca late 1320’s, having learnt his cartographic trade in Genoa. He was possibly still producing charts in the early 1340’s, as Chart C9 (London, Add.MS 25691) is dated to that period, although some scholars consider it may precede the 1325, C7 Chart. My ChCs/2 text also details this point as a possibility. However the change of date does not preclude the atelier continuing to the 1340’s and being the Cresque base, as the Cresque Chart is undoubtedly a copy of the Dulceto (!) charts. Therefore it is possible to opine that there is a linkage between the two ateliers.
The Cresques chart does however have two unusual features drawn thereon, one is quite unique, the second a copy feature, which are discussed in detail within this text analysis of the chart. It is then compared to the Dulceto (!) charts and other charts following the system developed for the ChCs/1 and ChCs/2 texts.

The text is 7 A4 pages and 11 (16) A4 diagrams.

June 2015
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The Portolan Charts that are available for testing as practical navigation aids are mostly highly decorated “library” charts, which although a visual feast are so complicated in their presentation as to be unsuitable for use in a dark cabin or ships open cockpit. It has been surmised by various authors1 that those used (if they were) on board ship were the same charts but with none of the decoration to obscure the main navigation elements. But are these charts actually an aid in any presentation mode, or are they an encumbrance through the methodology required to use them on board ship. But, were they actually used on board ship?

This text analyses the simple route from Majorca to Alexandria, Egypt, using two sailing methods; that of the Portolan chart via the magnetic compass and that using the geographical wind directions and natural phenomena, the Sun and Stars for guidance. The research cannot attempt to emulate every minor course change that was necessary and must therefore be a simple discussion that considers all methods equal and that deviations on each course will cancel each other out. There is no methodology or patent formula to allow for quirks in the sailing methods of the medieval sailors given that at various times of the year the route will require a different form of sailing for the winds and tidal flow in the Mediterranean Sea. Thus for this text, the wind is constant with no tidal deviation. However one constant used is the magnetic deviation for the period of 1300AD for the whole Mediterranean Sea, 5 degrees east to 16 degrees east declination.

There are 18, A4 pages and 11, A4 Diagrams for this text.

September 2015
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The accuracy of Portolan charts has been shown in my previous texts, ChCs/1 and ChCs/2 where I have compared them to each other and a geographical Mercator map.
But in 1987 J T Lanman wrote “On the origin of Portolan Charts” and within chapter 8, “A proposal for the origin of Portolan charts” he wrote 6 sections (large paragraphs) and a concluding paragraph. The 6 sections are Data Base, Projection, Skewing, Purpose, Distortion and Contemporary evidence.
This text illustrates that J T Lanman was misguided in his theoretical approach, when he concluded that an accurate chart could be drawn from the data within the coastal section of the text, “Lo Conpasso de Navegare”, when it patently cannot. He also concluded there was a magnetic declination used to plot the coastal courses within the text. Then he used a square grid for his reconstruction which has been shown to be nonsensical. The graticule is rectangular and although it appears to accord to a Mercator map, that is coincidental.
That his points are spurious is amply illustrated in this analytical text. It is necessary to point out though that J T Lanman used a text with many errors for the distances and bearings, and appears not to have cross checked the distances from the Peleio route distances which are multitudinous within the text and generally very accurate.
Thus I am able to add a postscript to this analytical text which has a surprising conclusion concerning the actual possibility of drawing a map from “Lo Conpasso De Navegare”. But it is nothing to do with J T Lanman’s theoretical charts.
This text is a précis of my complete analysis of “Lo Conpasso De Navegare” carried out to investigate the possible uses for the text and its accuracy. It concentrates only on the Western Mediterranean Sea area from the Pillars to Sicily, as a means of curtailing the text.

There are 23, A4 pages and 10, A4 diagrams.

September 2015
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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.

September 2015
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Having analysed “Lo Conpasso de Navegare” “Grazia Pauli” and “Liber de Existencia Riveriarum” texts to produce my text ChLCN/1, and then compared it to “The Carta Pisane” in text ChCpS/1, I concluded that the LCN text in its “Starea” section was unfit for purpose as the basis for constructing a chart. However, the Peleio section of LCN could be the basic data with which to draw a map or chart from the matrix that could be produced there-from. Although Peleio distances correctly positioned a large number of coastal features they required evaluating to determine if they were the actual basis of the Portolan Chart construction. But of course the LCN does not include the Atlantic Sea area!
Starting with the Peleio distance/directions, all +300 of them plotted on a series of maps, I concluded that a triangle formed the basic reason for the choice of node points. The points interlinked to cross locate from many of the coastal features. In fact a considerable number of the individual Peleio distance/direction notations were very accurate such that there could be NO magnetic deviation within the text details.
There were however many obvious scribal errors both for distance and direction when evaluated against a geographical map. Most could be shown to be attributable to poor copying, scribal error, but one section is solely responsible for the apparent distortion of the charts, which has led to the belief in a magnetic deviation.
My conclusions are that an original form of LCN Peleio data was used to draw the Portolan Charts. I believe the origin is probably from the Roman Period 300BCE to 300CE: there is no magnetic deviation at all in the charts draughtsmanship: the inaccuracy of the map plot is attributable to the mistaken distance measures from Sardinia to N Africa which imparted a bias in the map plot: the measurement used on the early charts is derived from the Roman Mile of 1.47911KM as one chart actually indicates.
This text cannot itemize every single Peleio; the majority are on the diagrams within this text and in the two previous texts, but where it becomes impossible to read alignments due to the sheer complexity of lines I have chosen for clarity of presentation to use a minimal number of Peleio triangle distances and thus simple Distance/Directional information.
I am sure interested parties will be pleased to draw the data for themselves and submit results. I also suggest the diagrams are downloaded, printed and joined to form large single maps (they are marked for that purpose) which will explain the twist and its false representation as a magnetic bent. It will also show that the simplest of presentations which have been misread as possible projections are nothing more than the result of drawing from a central alignment both east and west. Thus the natural positioning of a node point from the triangles causes the supposed projection. I repeat, there is no magnetic deviation on a Portolan chart!!

This text is 16 A4 pages and 29A4 diagrams. (29 pages as presented)

November 2015
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I have already subjected the Starea section of “Lo Conpasso de Navegare” to a detailed examination in text ChLCN/1, and followed it with a research paper concerning the Carte Pisane, text ChCPS/1, and then a major investigation of the Peleio section of LCN which illustrated in text ChCPC/1 how the basic forma for a chart could be constructed from the Peleio data and negated the idea of any magnetic interference in the charts construction.
This text uses three more charts, Cortona, Vesconte 1311 and Dulceto 1330 to investigate the continuation of the usage of an “LCN” text and compares the results to the Riccardiana MS3827 chart used as a reference point in the ChCPC/1 text.
The findings are that all use a version of the “LCN” text as the distance measures clearly indicate, but their draughtsmen or cartographers are somewhat different in their approach to the extant data c1300AD, which indicates several varying content copies of “LCN” then extant.
The Cortona chart is surprisingly accurate; it has hidden attributes. The Vesconte 1311 chart, although only of the eastern Mediterranean Sea basin is shown generally to accord with the “LCN” data, but it has been drawn from the east and thus shows a greater distortion derived from the spurious “LCN” data. The Dulceto 1330 chart appears to apply original “LCN” data for its construction and is the closest to it, hinting at a loss of early knowledge and thus the errors in “LCN” and a copyist approach to it.
The conclusions are as already posited in previous texts; the use of one or more copies of “LCN”; no magnetic deviation; obvious access to far greater detailed data than is now extant.
Included is the text ChEPC/1, an essay regarding the timescale for the original chart.

The text is 14, A4 pages and there are 27, A4 diagrams.

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Within previous texts, ChLCN/1, ChCPC/1 and ChMAT/1 it has been shown that scribal errors within the LCN texts in the area south of Sardinia led draughtsmen constructing Portolan Charts inadvertently to slew to the northeast the eastern section of the Mediterranean Sea. I have already utilized charts C2, Cortona; C3, Vesconte 1311; C7, Dulceto 1330 and C8, Riccardiana ms3827 within text ChMAT/1 and thus in this text utilize 10 further charts solely for their drawn area south of Sardinia to compare their usage of an LCN text. The dates vary from 1339 to 1464 and are from C9 to C65 in LCP.
The Starea Peleio abstracted from LCN numbers 73 routes of over 100 millara and is used to cross-locate ports in both the western and eastern Mediterranean Sea. The 10 charts are presented with their scale bars to illustrate the variation but mainly the continued use of an LCN text. Thus the slewing of each chart can be shown via the distance measures used, which vary as is discussed briefly for each chart, but, the obvious agreement between them indicates that the information they are drawn from is the same “Alpha Map” base, and “Alpha LCN” text, which has been mis-copied in certain sections.
In my short essay text ChEPC/1, I opined that the Peleio section of LCN was probably taken from the “Alpha Map” as they are impractical to observe as sailing direction/distance measures at sea. I then constructed a scenario, purely speculative, which indicated that the original Portolan Chart was much earlier than 1000AD and developed from a Roman Map and itinerary text. The theme of the maps usage and ancestry is continued in this text regarding the possibility of the Starea Peleio section being driven by the necessity, firstly of the routes to be used by the new maritime cities, and then of sailing for the Crusades which provided an impetus to increase, diversify and rename ports to suit the new age and the explosion in sailing. But many quirks are included on these charts to fool us.
Thus having completed a review of LCN and the major charts of LCP, C1 to C64 and confirmed the obvious fact that by using LCN Peleio distance directions, which all charts can be shown to agree with, there is no magnetic deviation involved, just the slewing caused by the miscopying of the LCN data, Roman Numerals for south of Sardinia, it became necessary to subject the two texts used by many researchers as the basis of the Portolan Chart storyline. I refer to firstly HOC/1/chapter19 text, particularly pages 380 to 386 which deal with the subject matter of my papers and then LCP (English section) pages 510 and 511(part) which are the similar subject matter. Pages 511 & 512 are dealt with in a following text, ChCOR/1.

The text is 18, A4 pages and contains 20, A4 diagrams.

February 2016
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The Cortona Chart is often linked with the Carta Pisane (LCP, C1) because of the perceived similarity of presentation, its draughtsmanship and the coastlines. In my text ChCPS/1, The Carta Pisane, I fully analysed that chart’s construction and its basic internal knowledge. This text analyses the Cortona Chart in a similar manner and juxtaposes “LCP” pages 511/512 text with my findings. The resultant research illustrates that there were a multitude of “LCN” type texts used throughout the first period of the “Library Style” Portolan Charts, following the end of what must have been a massive flotilla of ships virtually constantly at sea to service the Crusades and trade that went with them, but no doubt using smaller and easily handled maps and complementary texts, Portolani + Chart.
This text starts with the Black Sea area on the chart, discusses the separate scale utilised and then the textual data available which is not apparent upon the chart. A section of the text has already been published in ChMAT/1, and is here-in appended, un- revised but very necessary to complete the research which follows the prime discussion of the Black Sea area. I have also indicated the “distortion” positions within the chart which not only make it accurate in a serendipitous manner, but show its construction from an “LCN” text. Finally, the reason for the charts distortion is revealed, simple distance measure errors which combined to visually confuse previous researchers into thinking there was a magnetic element; there is not. But why the draughtsman chose to use two differing scale bars can be answered only speculatively. As an extra discussion the Black Sea is investigated in a short essay reference ChBLS/1. The same change of scale on other charts and atlases and the actual form that can be obtained from the” LCN” text is drawn, which confirms the fact that a “Alpha Chart” was available and several “LCN” texts of varying quality.
Draughtsmanship before history and you will solve a great deal more far easier!

The text is 13, A4 pages and 8 + 6 + 10, A4 diagrams (24 in total from 3 sections of text).

March 2016
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Many researchers have written texts which in part discuss the work of A. Dulceto, and imply the finding of magnetic declination, magnetic compass usage to plot the charts and differing projections used to draw them.
I have chosen therefore the same chart, A. Dulceto 1339 (LCP C8) held by the BNF Paris as the base data with which to counter those theories existing in the four texts to be analysed. The chart is first dissected to indicate its fundamental structure and the varying scales used from west to east, Ptolemaic Degrees, Millara, Roman Miles and Marritimo Miglio, as well as the reasons for its skewing. The link from Rome via Claudius Ptolemy to the Millara is clearly shown and thus the origins of the “Portolani” and its accompanying chart are confirmed. Any researcher who has read my previous papers will not be surprised at the findings, quite incontrovertible, as they are merely the data the chart exudes, and thus will understand why I have not written reams of text in explanation of my findings for this 1339 chart. But the intervention of the Ptolemaic degree is surprising and is resolved by the explanation of the various distance measures within a Portolan chart.
Please note that prior to the analysis of the four texts, I have inserted a short but very necessary note regarding the use of Cartometry, Formulae and Computers to analyse a Portolan Chart and thus end up with bland averaging and an incorrect analysis of the chart.
The four texts are, J A Gaspar, ePerimetron, 2008; W R Tobler, Am Geog Soc, 1966 and 2007; J E Kelley jr. Cartographica, 1995; and C Boutoura, ePerimetron, 2006.
The results of this critique are expressed quite directly and thus I would advise caution when future researchers may wish to utilize them; I consider them to be lacking.
NOTE: I am still awaiting a researcher to explain how the magnetic compass was used to plot the courses and then, how the pilot book data led to a Portolan Chart to be drawn. It has been stated again in 2015 that “owing to the navigational methods of the time, which were based on magnetic directions and estimated distances”, that research is so very necessary. Why the “Pilot Books” extant do not use magnetic data requires answering.

The text is 22, A4 pages and contains 23, A4 diagrams.

April 2016
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The chart is obviously an excellent example of the genre, but it is also obviously an amalgam of two schools; Claudius Ptolemy and a LC de N derived Portolan Chart. The western section from Britannia southwards through France, Iberia to N. Africa is drawn to the Ptolemaic dictum as expressed in the prologue to Book 2 of “Geographia”, a simple proportion and rectangular graticule. But this only applies from 9W to 3E where the L C de N format then becomes apparent and the usual errors around 9E longitude skew the chart to fool some researchers into the magnetic declination school of thought. However the main problem can be observed at Bugea (Bejaia) on the N. African coast where the distortion is so apparent.
The eastern Mediterranean Sea is drawn quite accurately but expanded to agree with the L C de N Black Sea over length such that the chart is in proportion at this point.
The chart is an exceptionally well presented Portolan Chart which indicates a growing knowledge of the mathematics involved and the greater accuracy of measurement. Thus the cartographical draughtsman can experiment with the latest (although 100 years earlier) ideas as promulgated by Claudius Ptolemy in the then translated “Geographia.” But it should be borne in mind that the whole genre of Portolan Charts has always in its background had the Roman measurements and Ptolemaic proportion within the makeup of the chart. However, still after +200 years it is evident that the “Portolani” texts are obviously still being used.
Unfortunately, the Butterfly did flap its wings to cause enough Chaos in the finished chart to be noticeable, which is actually a sad occurrence for a thing of some beauty.
I have chosen to juxtapose this chart with a short text regarding two charts, Jorge de Aguiar, 1492, and Pedro Reinal, 1504, which show the partial development of the Iberian Peninsula as a rectangular graticule. The Pedro Reinal chart has the fully formed latitude scale in a similar position to the Jacobus Russus chart and thus they can be compared. This text was originally indexed as ChMES/1 and has 7, A4 pages and 6, A4 diagrams.
This text contains 6, A4 pages and 16, A4 diagrams which all interlink in their series.

Totally the text is 13 A4 pages and there are 22 A4 diagrams.

May 2016
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PORTOLAN CHARTS OF 1413, 1436, 1448 & 1463/9; THEN CAPE VERT AND 3 LETTERS FROM 1495


The exploration of West Africa from the Strait of Gibraltar to the Gulf of Guinea is a story of two or three parts. Firstly we have the recorded voyages pre our common era, and then apparently nothing south of the Canary isles until the Portuguese explorers ventured forth in the 15th century. Thus the second part may be described as the scramble by Portugal and Spain to land grab as much as possible. This caused friction between the two nations and was eventually solved (!) with the agreement reached at Tordesillas in 1494 (among others) and thus we have the letters of 1495 endeavouring to explain it all cartographically.
But all of that ignores the large Arab presence, their knowledge of the coastline and the fact that it was transmitted to N. Africa and thus the Iberian Peninsula in the 10th to 13th centuries. Finding the information however has proven nearly impossible, hence the following methodology, as even the text of Al-Idrisi shines little light on the knowledge. Thus this text uses the Portolan charts/atlases as a means of illustrating the knowledge gained in by the late 14th and early 15th centuries, how it affected the presentation of the knowledge and the gradual correcting of the spurious data which so affected them.
Obviously, between the 1413 and 1436 charts the work of Claudius Ptolemy intervened and affected presentation. The letters of 1495 illustrate the confusion reigning at the time over distance measures from the ancient metrologies, and the utter disregard various countries had for each other’s measurements, even though a single measure was available. This text therefore also tackles the vexed question of the confusion between the Millara and the Roman Mile and presents a reasoned argument for the Millara origination, no not 5/6ths.

The text is 21, A4 pages and contains 26, A4 diagrams and 4 appendix pages.

February 2017
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The Petrus Vesconte 1311 chart has featured in several previous texts, but has never been subject to a complete internal structure evaluation. This text merely corrects that omission and illustrates the accuracy which can be found longitudinally and the obvious latitudinal faults which appear to follow through to most extant Portolan Charts of later date. Those faults are distortions and are clearly set out in various papers but will be detailed here-in to define the charts. The wind rose system is the setting out and has been adequately shown to be the arbiter of the plot via its measurements. The atlases, concentrating on the 1313 and 1318 work indicate conclusively that the typical distortion of a Portolan Chart, basically shown as being from Iberia to Italy, could have been avoided by the correct application of distance measures for Iberia and from Genoa to N. Africa and a full understanding of the measurement of a degree which varies even though the name of the unit is the same. But the problem of the scale bar being firstly a Roman Mile and then considered a Miliaria can be shown to be the main cause of the deviation of the latitudinal and longitudinal lines to enthuse historians to conclude that the distortion was a magnetic deflection, Just how wrong they could be is illustrated here-in. Various other small charts are illustrated for continuity of the works by Petrus Vesconte.
There is finally an appendix which illustrates the whole distortion scenario, how it occurred and the consequences for Portolan Charts, with after words that require to be said!

The text is 15 A4 pages and has 28 A4 diagrams.

August 2017
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Having studied a large number of Portolan charts, as the website clearly shows, I was struck by the lack of examination of extant Atlases in the research texts of others. Those Atlases are detailed in Les Cartes Portolanes, pages 69/70, and having just reviewed my research into the work of Petrus Vesconte (ChPV/1) and revisited his Atlases, I decided to review my research including those Atlases and others, not all of them, just the first 14.
However, I did not consider that a short text could contain a complete review of those chosen as I had carried out on the Petrus Vesconte 1313 and 1318 Atlases, but instead concentrated upon the Atlas page containing the Iberian Peninsula, the starting point for the utter confusion which can be shown to exist apropos distance measures and thus the original distortion point for Portolan charts.
As there is generally only one scale bar to each Atlas page, it is thus a simple matter to ascertain the accuracy and measures utilized to draw each sheet. Thus, when a confusion of distance measures is encountered on this one Atlas Page, emanating from a single scale bar, little more than those facts require to be investigated. It also determined that the draughtsmen were not au fait with their subject matter and thus should be considered only copy artist’s, but from what? That does not infer criticism of the artistry to produce these Atlases as they are a feast for the eyes, and illustrate exquisite draughtsmanship but a lack of real knowledge, and confirms they are copies, not original works. How many originals were copied is detailed.

The text is 11, A4 pages and contains 16, A4 diagrams (some are text based).

September 2017
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Having analysed the Atlases LCP A1 to A14, concerning the Iberian Peninsula and established that there was a complete lack of knowledge apropos the actual distance measures utilised and that the unit of measures were also confused, it was necessary to proceed along the time line for Atlas Charts to further our information concerning their inner workings and establish if the problems encountered were in fact solved.
Hence as the BNF Paris had excellent scans of the Atlases by Diogo Homen and that fortuitously they had featured in my first Portolan Book from Thames and Hudson, I knew they would shed light upon the subject. Thus a complete analysis of two beautifully drawn Atlases by Diogo Homen was undertaken, as well as an analysis of one of his excellently drawn Portolan charts, to establish the extra knowledge gained over the ensuing +100 years from 1434 to 1559AD. Unfortunately the results were very disappointing and add little to the original data which has been compiled as the problems persisted with no new knowledge.

The text consists of 6, A4 pages and contains 17, A4 diagrams

October 2017
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Throughout previous texts I have shown that the inner workings of Portolan Charts and Atlases indicate several distorting factors which have the effect of slewing the chart anti-clockwise from c3 to c11 degrees. That difference can be evaluated as the accuracy of the charts author in his draughtsmanship. But a study of the Iberian Peninsula showed that the basic slewing was in fact c12 degrees and emanated from one single fact; the draughtsman had used two distinct measurements for a degree of latitude which are in fact the same measurement in different forms but had used a single scale bar to measure them, thus totally ruining any accuracy that may have been possible. Therefore the Iberian Peninsula has the in-built potential to totally slew the whole chart by c12 degrees.
But that appeared to be a rather curious situation akin to the tail wagging the dog.
Thus I considered that the problem is in fact the opposite; that is, the chart was first drawn with a 12 degree slew anti-clockwise, then the Iberian Peninsula was tacked onto the chart, which would be correct if it was, as I have suggested previously a Roman Map. As the Roman World expanded the chart grew to encompass all of their lands and thus was not necessarily at first a full Mediterranean Sea basin map, but evolved from several forms.
Marcus Vipsanius Agrippa produced a “world” map in c11BCE following a “world survey” instigated by Julius Caesar in c54BCE, and that map was displayed in Rome.
Thus using extant Roman Texts this paper sets down the scenario for the 12 degree slewing of one of the original Roman Charts and how it developed into a Portolan Chart.
I have added to this text the work by Joan Blaeu, not for his charts but for his written words which discuss many of the problems I have uncovered.

This paper contains 19, A4 pages and 17, A4 diagrams.

November 2017
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A fellow researcher kindly sent me a copy of his paper regarding the “Enigmatic Chart” by Baldassare (Maiolo) Maggiolo, dated 1589 which appears to be drawn as four atlas pages each rotated 90 degrees from the next thus forming a rotating vista. That original text (q.v.) is predicated upon pixel measurements which to my draughtsman skills implies accuracy far in excess of that achievable in the 16th century, and does not allow for the vagaries of the charts actual drawing which was to be explored. My interest was thus piqued and I decided to explore the charts inner working and format which was made even more fascinating as the original text included a thumbnail copy of the Munich chart from Sir Robert Dudley’s Dell’Arcano del Mare. That original text stated “une carte tres similiare”, but then ignored it.
Thus there are two “enigmatic charts” which together may answer the question regarding their extraordinary presentation I therefore explore both, and with their idiosyncrasies endeavour to explain their raison d’être. The original text, chart and Munich chart are appendix notes.

This text contains 9, A4 pages and also 30, A4 diagrams.

December 2017
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The text is in two distinct sections; firstly an analysis of the chart dated 1500 noted as being by Juan de La Cosa to understand how it was drawn, the measurements used and the probable origination of the data used; and secondly an analysis of the “raw” historical data regarding the “La Cosa” personage and his exploits after stripping out the hyperbole and extravagant overstatements of many authors who have written concerning the whole subject of the exploration of the West Indies.
Both sections are written as stand-alone texts and need not be read as one paper.
This section casts doubt upon the authorship of the Chart and perhaps the date appended, as it appears to have information that was only known after the 1500 date and is thus thought to be 1502 at the earliest as others have suggested, but in fact could be even later. This section also questions the charts origination. The second section is merely the historical facts that can actually be accepted as such. But, as only confirmed fact should be used before accepting circumstantial evidence, and there being little definitive data to go on, speculative texts abound and they must be challenged. Both sections have their own Abstract/Introduction and they are not cross referenced to each other to allow the reader to reach his or her own conclusions from the evidence presented.

The part one text is 13, A4 pages and contains 28 A4 diagrams. Pages 1 to 13.
The part two text is 8, A4 pages and contains 1, A4 diagram, D01 from above. Pages 14 to 21.

March 2018
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Having read many texts concerning the Columbus exploits and thus knowing of Juan de La Cosa from those texts and his c1500 chart, I was totally bemused by the chauvinistic approach of many authors and how in each text new titles appeared when the historical facts did not actually agree. It appeared to me to be a little massaging and improving the data.
Thus I decided, but against my better judgement and contrary to my normal approach of analysing charts and maps, to explore at the most basic level the history appertaining to Juan de La Cosa. As has been stated by others, there is little hard evidence (or none in reality) regarding him prior to 1492. Even where he was born, his home village has been guessed by some when it is clearly written in a ships listing, but to establish the credentials of the c1500 chart the investigation is necessary.
In the first section I analysed the chart by draughtsmanship detail and now the second part is an analysis from confirmed facts with a timeline to establish the whereabouts of and the survey work Juan de La Cosa could have carried out.
Please note that to simplify references I am giving only page numbers from “Christopher Columbus, An Encyclopaedia”, edited by Silvio A Bedini, which was originally published in two volumes in 1992, but re-issued in 1998 as a single volume which is here-in used. I have and have also read numerous other texts and find that the basic facts remain the same throughout with some “gilding the lily” regarding the situation and others stretching facts to breaking point; one is enough!

The part two text is 8, A4 pages and contains 1, A4 diagram, D01 from above. Pages 14 to 21.

March 2018
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The Planisphere copy has garnered many plaudits from the historical and cartographical communities for its sumptuous presentation and scope of its geography. Many historians and cartographers have written treatises concerning its contents and endeavoured to illustrate that which it portrays through technical means.
Each and every one of these researchers has completely missed the most obvious and determining part of the design by generally adhering to preconceived ideas, instead of detailed analysis of the actual chart and its construction.
This text shows that the original Portuguese cartographer was a master artist and mathematician/geometrician who understood the necessity for constant measurement, but was thwarted by the data given which obviously consisted of a myriad of measurements named the same but wildly differing. Add to that the inability to transcribe Arab “Kamal” readings to either distance or latitude and only draw what was described thus the problems mounted.
The Planisphere copy must be investigated section by section to expose the problems the cartographer encountered, but overcame, to produce this feast for the eyes.
One question I fear will never be properly answered however is, “just how accurate is the copy we are now studying”? Personally I suspect that it is not copied, but the work of the original atelier, or persons of the original atelier and thus it is probably very accurate and the distance measures originally used are perfect, as the wind rose graticule which is so very accurately constructed illustrates.
Being produced by the original cartographic atelier, or those cartographers, it would explain other problems encountered in the research. That idea is very plausible as will be adequately indicated within the text pages.
Note; I have used my copy of the CD-ROM from Biblioteca Estense Universitaria for the Cantino research and diagrams illustrated. It was produced by Il Bulino + Y Press, 2004.

The Caverio 1505AD Planisphere has been variously quoted as being copied directly from the Cantino 1502AD, or as having very similar origins. Those are probably copies of copies of the “spare” planisphere no doubt kept by the original atelier for future charts to be drawn from. That it is a copy of a Portuguese chart is undoubted from its toponyms and content, but the chart requires to be analysed to ascertain its inner workings as they are not the same. The final analysis however must wait for the next text, ChFANO/1, which indicates that the chart is a pastiche of several charts and was probably started in Lisbon and finished in Italy.

The Cantino text is 10, A4 pages and contains 17, A4 diagrams.
The Caverio text is 6, A4 pages and contains 15, A4 diagrams. (total text 16 A4 pages)

April 2018
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It was a finely drawn chart which even in its present state of washed out presentation has many attributes, but, obviously the chart has been reduced in size to 1395 x 910mm, and before any investigation into its actual geographical portrayal takes place there requires to be an investigation to determine to what extent it has been reduced and thus what is “missing” such that a correct appraisal of the chart can be undertaken, This has been achieved using the wind rose graticule and its setting out. This I perceive nobody has bothered about before!
Then the drawn chart is analysed and compared to other charts which numerous researcher’s state quite frequently is probably a copy of the Cantino Planisphere or its derivative but it can clearly be shown to be from a different source chart. Finally the vexed question of attribution and date is addressed from viewing the actual script on the chart.
The text is 8, A4 pages and contains 21, A4 diagrams (A3 originally).
The postscript contains 26 photographs which were supplied by Biblioteca Comunale Federiciana at FANO of parts of the chart and are an excellent aid to studying its content.

June 2018
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Being unattributed upon the parchment itself, the format has led to many researchers speculating ad infinitum regarding its draughtsman/author.
Visual inspection can be self defeating when one chart is 1140 x 1790mm and the other perhaps only half that size. In that situation the eye of the beholder can be seriously misled. Thus this text sets down the investigation of the Pesaro Planisphere into its inner workings and compares it to those other charts speculated as being similar or perhaps by the same author, but the research uses the various chart forms as the arbiter of similarity with actual overlay illustrations.
The Pesaro Planisphere is beautifully drawn, is a one off in several respects and does not appear to be by any of the speculated draughtsmen/authors; but is it finished?
Note; this paper is a diagram based paper with limited but concise text, thus the diagrams should be carefully studied to ensure the various layers are fully understood. The diagrams numbers 15 to 24 are in fact 3 charts and they can be joined together by the overlapping areas to illustrate the complete comparison of chart to chart.( A4>A3)

The text is 06 A4 pages and contains 28 A4 diagrams, all of which commenced as A3.

August 2018
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Henricus Martellus 1491 and Martin Waldseemuller 1507 charts both exhibit a peculiarity in the draughtsmanship design of the African Continent. Thus it appears they were both confused by a similar presentation of a plain rectilinear chart they were using to draw their curvilinear world maps or charts. The reason for the confusion is amply illustrated by the King-Hamy 1502 chart which has two Equatorial lines; one for the western geographical section and one for the eastern Ptolemaic section, but they are shown as overlapping within the African Continent.
Also to be addressed is the confusion with the nomenclature researchers have used to describe the form of these charts. They are not cordiform or Pseudo-Cordiform but plain Ptolemaic projections as can be amply illustrated. The Martellus 1489 printed charts are nothing more than an inverted Ptolemaic First Projection and then the 1491 chart and the M.Waldseemuller 1507 chart are just a slightly modified Projection Two by Ptolemy.
Thus this text commences with the Geographike Hyphegesis of Claudius Ptolemy, explores the King-Hamy 1502 chart (D01), then an analysis of the Martellus 1489 printed charts (D02) and finally the Martellus 1491 chart (D03 & D04) and the Waldseemuller 1507 chart (D05). For all of these answers are given to the questions regarding draughting methods, construction and their presentation, including their errors and foibles.

The text is 15, A4 pages and contains 59, A4 diagrams (all originally A3)

September 2018
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Read research papers or books concerning Genoese 14th to 16th Century cartography and there is not one text written which investigates how it all happened and uses simple basic facts such as lifespan, training or raison d’être for the origination. The first extant work provable by attribution is that of Petrus Vesconte and his 1311 chart. But he had to be taught the art and that has never been addressed in the myriad of papers written over the last years. Add to that the Carta Pisane, probably 1290 and the Cortona Chart c1300, both of which have doubtful provenance, but by existing they push the date backwards for the training of their authors. Thus this text sets down clearly known facts and dates and uses the life spans attributable to evaluate the overlap of these cartographers and how their charts also spring from a basic pattern/template which is amply illustrated in the second part of this research.

The text is 20 A4 pages and contains 53 A4 Diagrams (originals are all A3, and some interlink to form the complete chart at large scale.)

December 2018
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