1652

WIND ROSE CONSTRUCTION ON A PORTOLAN; REVISIONS TO THE ORIGINS OF THE CHARTS FORMAT AS DRAWN.

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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1674 1804

USING A PORTOLAN CHART AT SEA; DID THEY? ARE THEY PRACTICAL OR IMPRACTICAL FOR USE BY MARINERS?

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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1818 1903

MELANGE A TROIS AVEC L’UNE, MS 3827; CORTONA; VESCONTE 1311; DULCETO 1330

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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1942 1946

10 DISTORTED CHARTS –LCN PROBLEMS CRITIQUES; HOC/1/19 p380-386 & LCP p 510/511

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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1971 2040

JACOBUS RUSSUS, 1533 CHART; CHAOS THEORY, NO! EXPERIMENTAL & EVOLVING DRAUGHTSMANSHIP, YES!

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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2067 2070

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

ABSTRACT

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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2281 2504

PESARO OLIVERIANA PLANISPHERE, c1509 RARE PRESENTATIONAL METHOD THAT GOES AWRY

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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