Talk:Portolan chart

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1295 is the thirteenth not the fourteenth century— Preceding unsigned comment added by Iglonghurst (talk • contribs) 08:13, 26 August 2006

Where does the name Portolan come from? Anybody know? Isoxyl 04:04, 26 January 2006 (UTC)Reply

"Initially the preserve of Mediterranean fisherman's firsthand knoledge of the seas and coastlines. Whereas the Mappaemundi were cartographic representations of medieval culture these where closer to contempory maps. Initially they focused on the Mediterranean zone and were comparatively rudimentry, they soon became refined until they surpassed the maps of the learned geographers."

Someone put an unsigned comment in my talk page about substituting "raiding" for "trading." The answer I gave there reads as follows: "You are certainly aware of Francis Drake and his privateer activities. Spanish galleons carrying silver were routinely attacked in the Caribbean and Central America and that is not a Hollywood myth. And when Portugal, 1580 to 1640, was under Spanish rule, Portuguese fortresses in Brazil were frequently attacked by the Dutch. I have a book written by a scholar on the subject documenting such activity, but because it is a bit long, and I do not have much time to put into reading at such lengths, I have been postponing it. The book is not in Amazon, an English translation seems not to exist, and Portuguese booksellers say the book is no longer available for sale. You can see that here http://www.wook.pt/ficha/o-grande-livro-da-pirataria-e-do-corso/a/id/107133 If I get around to read it, I will walk Wikipedia a bit with the information gleaned."

The historical rationale is that the English and Dutch navies began with raiding, and only when the Spanish and Portuguese Armadas lost hegemony, did English and Dutch trading ports started being established. Deep Atlantic Blue (talk) 19:29, 7 June 2010 (UTC)Reply

A Portolan chart is picture of the day (10 June 2011), showing this text: "A portolan chart from 1492, the oldest known signed and dated chart of Portuguese origin. Cartography technologies greatly advanced during the Age of Discovery. Iberian mapmakers in particular focused on practical charts to use as navigational aids. Unlike Spanish maps which were regarded as state secrets, Portuguese ones were used by other countries, and Portuguese cartographers drew upon the skill and knowledge of other cultures as well."

Whereas this page contradicts that text: "With the advent of the Age of Discovery, they were considered State secrets in Portugal and Spain" — Preceding unsigned comment added by 76.126.215.43 (talk) 16:36, 10 June 2011 (UTC)Reply

several of these charts seem to have the writing 'upside down' as though the older orientation had north at the bottom of the page? have I got that right? is it mentioned anywhere ?EdwardLane (talk) 11:33, 30 September 2011 (UTC)Reply

• Most portolan charts didn't have a 'correct' orientation though they were commmonly exposed with north up when hanged. The geographic names (toponyms) were written perpendicular to the coastlines and followed their orientation. Alvesgaspar (talk) 12:08, 30 September 2011 (UTC)Reply

I'm a specialist on early portolan charts. "One of the world's greatest and most enduring mysteries" like the Washington Post wrote May 22, 2010. On my user page I created several subpages that explain and discuss a lot of issues around portolans. Unique rare images and graphics are presented. Some published for the first time. I came from the German language tradition of portolan research. That is more focused on the scientific or engineering aspects, on mathematic and cartometric analysis. It traditionally suggests a Roman or Greek time origin. The present English language tradition is less mathematical and suggests a sole medieval origin.

My pages offer most English speakers for the first time the cartometric arguments about the portolans. Beginners should first read "What is unsolved about portolans? The Problem of the Portolan Charts". The pages are with lot of explanations and therefore not intended to be direct copied in the article space. Rather someone with interest on the subject and Wikipedia experience should decide what may be appropriate here. -- Portolanero (talk) 16:55, 16 December 2011 (UTC)Reply

I have reverted the new material inserted by Stan Lusby on the origin of portolan charts, based on non-main stream research, because it contains serious historical and technical mistakes. Please check the chapter by Tony Campbell on the 1st volume of the History of Cartography (1987), the excellent book by Ramón Pujades (2007), 'Les cartes Portolanes', and this article by Joaquim Alves Gaspar (2008): [1]. It is now consensual among researchers that portolan charts were developped in the begining of the 13th century, in the Medieterranean, and were constructed on the basis of magnetic directions given by the compass and distances estimated by the pilots. It is also false that later nautical charts were based on the Ptolemaic system of latitudes and longitudes: latitude charts, developped by the Portuguese near the end of the fifteenth century, were based on observed latitudes and magnetic courses. This well well documented in textual historical sources and confirmed by the quantitative analysis of the charts. Alvesgaspar (talk) 09:53, 2 June 2013 (UTC)Reply

I saw a presentation about the recent hypotheses that the portolan charts are definitely using the mercator projection and came here to read about it, only to find nothing. Is there truly such a consensus regarding this that it doesn't even deserve to be mentioned in the article? — Preceding unsigned comment added by 162.232.246.7 (talk) 06:23, 8 March 2014 (UTC)Reply

The article Rhumbline network is mainly about portolan charts, and is rendered doubly redundant by the article Rhumb line. I propose merging its content into this article. RockMagnetist(talk) 15:59, 20 October 2015 (UTC)Reply

It would be incorrect to merge Rhumbline network to Portolan Chart for there are plenty of mapamundi that use the Rhumbline network and by no means can be considered portolan charts ('they do not have any PORT-harbour on them')

• Map_of_Juan_de_la_Cosa
• Cantino_planisphere
• Teixeira planisphere

--Mcapdevila (talk) 21:34, 20 October 2015 (UTC)Reply

Would it make sense to merge it with Rhumb line, then? RockMagnetist(talk) 21:50, 20 October 2015 (UTC)Reply

The assertion:"Rhumbline network is rendered doubly redundant by the article Rhumb line" it's not exact.. for its primitive name waswinds network (from italian griglia dei venti) not related at all to the english concept developed in the rhumbline article they are just false cousins using the same name(600 years away from each other).. I've added it to the article to avoid misinterpretations..--Mcapdevila (talk) 22:28, 20 October 2015 (UTC)Reply

I'm not convinced. In Rhumbline network, I don't see any definition that would distinguish the lines from rhumb lines.The existence of an Italian term for it is no evidence that it is really different. In Portolan chart, rhumb lines represent constant compass directions. The definition in Rhumb line is equivalent, but more general as it applies to ocean crossings as well. RockMagnetist(talk) 00:44, 21 October 2015 (UTC)Reply

Then we should have to merge it with both rhumb line and orthodrome.. In the Med for the portolan your assertion would be true but not in the planispheres (wich do not follow the mercator projection) If one "submerges" its eyes into the catalan or italian maps of that time and studies them (I've been doing it for the last 55 years, my father made me a present of a facsimil of Cresques planisphere in my 15th aniversary 23-10-1945).. one is able to read the names of those lines wich were winds: Tramontana, levante, ponente, mezzogiorno, greco, sirocco,lebegio.. together one can see that they follow both rhumb line and orthodrome or neither of them, due to the imprecision of the map making of that time, being the rhumb line only almost true in the Mediterranean portolan charts and a complete mess (for its in-exactitude) in the Texeira planisfere (and the others mentioned before)

Today, after the mercator projection, we have two concepts clearly distinct loxodromic navigation and orthodromic navigation and the thousands of english speaking sailors (as my coleague and sailing friend Rodney Pattisson), map makers, etc.. they know perfectly that fact..--Mcapdevila (talk) 08:31, 21 October 2015 (UTC)Reply

I'm impressed by your knowledge of maps, and would like to be sure that we come up with a solution that you agree is correct. I think the main issue is, what is a rhumb line? If that is settled, then a rhumbline network is just a network of rhumbs, and not really a separate concept. We need to answer this question for the English language; maybe the meanings are different in Italian, but that's not relevant here. For convenience, I am going to quote the Oxford English Dictionary meaning. Rhumb line is equivalent to the first sense of rhumb, which is:

1 a. The line or course followed by a ship or other vessel sailing in a fixed direction. Also: an imaginary line on the earth's surface intersecting all meridians at the same angle and used as the standard method of plotting a ship's course on a chart

(I'm not sure what a "fixed direction" means if it's not based on geographic or magnetic meridians.) RockMagnetist(talk) 17:29, 21 October 2015 (UTC)Reply

I don't think the distinction between loxodromic and orthodromic navigation is relevant here; even in modern navigation manuals, a rhumb line is clearly identified with constant bearing, never with great circles. See, for example, the Admiralty Manual of Navigation and The Flight Navigator Handbook. Similarly, some directions may have been associated with winds, but wind directions aren't very reliable. Correct me if I'm wrong, but I would guess that in the Cresques planisphere, the directions for the lines were chosen by some other method, after which the wind labels were added. RockMagnetist(talk) 17:29, 21 October 2015 (UTC)Reply

• There is some logic in RockMagnetist's reasoning. However he departs from the false assumption that only portolan charts depict rose-wind systems (this is a better way of calling it because those lines are not true loxodromes). The fact is those systens of lines (rhumbs) irradiating from certain points of the charts were adopted in other cartographic models, such as the latitude chart of the Atlantic (from about 1500 on) and even the Mercator chart (from 1569 on). I agree that the distinction between loxodromic and orthodromic navigation is not relevant here. Only in 1537, in a treatise of the mathematician Pedro Nunes (Treatise in defense of the nautical chart), was such distinction made for the first time. Anyway, orthodromic navigation was (and is) seldom used by mariners (I know, I am a navy officer). I hope these considerations help. Alvesgaspar (talk) 20:42, 21 October 2015 (UTC)Reply

At the end some clever words from Alvesgaspar that I think should clarify the case: "..rose-wind systems (this is a better way of calling it because those lines are not true loxodromes)..".. I have created loxodromic navigation and orthodromic navigation to explain that it was with the mercator projection (1569), that a rhumb line could be represented by a straight line.. rose-wind lines from the portolans (1275).. are straight lines.. therefore -for Reductio ad absurdum- they can't be loxodromic (today's rhumblines).. otherwise the mercator projection would have been invented in 1275..they are false friends (inside english language) that lead RockMagnetist to the actual confusion.. By the way... it would be of interest reading the doctoral paper of Mr Hurtado where he explains the portolan projection as the addition of multiple azimuthal projections with multiple centers -like today's Google maps- (the best explanation-theory I've found in 55 years)... but this would be like opening Pandora's box..--Mcapdevila (talk) 06:36, 22 October 2015 (UTC)Reply

Alvesgaspar, Mcapdevila: If anything, I am more confused after all this explanation than before. I'm finding it difficult to see just how the above considerations apply to the question at hand - should there be an article rhumbline network, or should it be redirected somewhere? Are there English-language sources that call the rose-wind lines "rhumblines" when they are not loxodromic? Should the article redirect to Rose-wind network instead of the other way around? RockMagnetist(talk) 01:43, 28 October 2015 (UTC)Reply

RockMagnetist, please study alvesgaspar very ..very interesting paper with proven knowledge and your confusion will vanish, then I think you will realize that it's beter for en.wiki to leave the article rhumbline network as it is (& pse. remove the merge label),..for what Bagrow says

By the way.. it's a fact that there are "Lines" in the windroses.. so.. how do you want to call them other than "windrose lines"?(forget Rose-wind that I like but maybe doesn't exist.. so I've changed it..)..Therefore, we don't need any English-language sources to call "windrose lines" some lines that are forming a windrose.. the same happens with "windrose network" that it's a network composed by a few windroses. It's the essence of English-language, isn't it?--Mcapdevila (talk) 08:59, 30 October 2015 (UTC)Reply

RockMagnetist, there isn't worst blind that the one doesn't want to see.. ,they are false friends.. using your linguistic argument we can end like the spaniard who translated (s.XVII) "Canal de la Manche" (Sleeve in French) for "Canal de la Mancha"(Stain in spanish) instead of Manga.. the article rhumbline network can not be merged to rhumbline (which 'today' is phisicaly a loxodrome), because, to be loxodromes, the straight lines drawn in the portolan charts... they should be outlined on top of a "mercator projection map -or similar-" (1569) and we have a fact agreed by all scholars: "they aren't outlined on top of a "mercator projection map", therefore, they couldn't be loxodromes in the XIII, XIV, XV centuries.. (see my previous reductio ad absurdum).. Do you realize the time we are wasting here instead of doing some more positive work?..As I have done adding a definitive reference to the "articles in question" and to Catalan map.. As leo Bagrow states:"..the word ("Rhumbline") is wrongly applied to the sea-carts of this period, since a loxodrome gives an accurate course only when the chart is drawn on a suitable projection. Cartometric investigation has revealed that no projection was used in the early charts, for which we therefore retain the name 'portolan'."--Mcapdevila (talk) 08:05, 6 November 2015 (UTC)Reply

RockMagnetist, the first problem here is that the term “rhumb” had no precise meaning when it came into use. It applied equally well to the windrose lines as it did to loxodromes because the term only applied “locally” and only meant whatever a sailor did in order to sail with constant bearing, with all the imprecision that that implies. Therefore “rhumb” was applicable to the straight lines on portolans when portolans were in use, as well as always applicable to straight lines on Mercator charts. For short distances portolan “rhumbs” do not meaningfully differ from Mercator rhumbs, but these days “rhumb” is synonymous with the mathematically precise “loxodrome” because it has been made synonymous retrospectively.

I do not believe “rhumbline network” is a real term (I defer to Alvesgaspar here) and therefore there shouldn’t be an article by that name. The Rhumbline network article needs a huge amount of work in any case. It may merit remaining independent precisely to explain the historical context and why the portolan network is not quite the same thing as a network of rhumbs. The article should be referenced from Rhumb line, Portolan chart, Mercator projection, World map and wherever else. The important concept it captures is the network of straight lines on maps intending to show sailing routes (without truly implying a precise path), as well as windrose networks. Those networks do not mean the same thing (mathematically) on every kind of map, but graphically they are all the same thing. Therefore the article describing them should make the history and purpose of such networks clear, but also make clear that they do not describe quite the same thing on each kind of map. Strebe (talk) 15:25, 6 November 2015 (UTC)Reply

• I agree in general. However the proposal was to merge the article with Portolan chart, which would be incorrect since those wind-rose systems were also depicted in non-portolan charts (e.g. latitude charts and Mercator charts). Alvesgaspar (talk) 16:39, 6 November 2015 (UTC)Reply

Sorry it has taken me so long to reply. It has been difficult for me to find the time to think about how to sort out this confusing tangle. Let me start by discussing a few facts about articles. First, rhumbline network is in the See also section of several articles, but it is only linked in the text of two, Portolan chart and Catalan chart. Those two, plus the section Rhumblines vs. windrose lines, have identical text referring to windrose networks and windrose lines (both of which point to rhumbline network, making a closed loop from the latter section).

The other thing to note is that Rhumbline network is a pretty mixed bag. Its heart is the section on network design, which is mostly about wind roses; much of the information is already in Compass rose (Wind rose is reserved for the meteorological term). Vellum map creation process also duplicates some of this information, and says very little about vellum itself. Planispheres with double hexadecagon is just a couple of images of Cantino planisphere and Teixeira planisphere, which have their own articles. And finally, Use of rhumblines is a sentence fragment. In short, there really isn't anything here that isn't better deleted or moved somewhere else.

Strebe: The best place to discuss the history of the term "rhumb" would be Rhumbline. Alvesgaspar: I agree that a redirect to Portolan chart is not the best idea, and there doesn't seem to be any support for it anyway. I will therefore change the target to Compass rose. RockMagnetist(talk) 07:26, 8 November 2015 (UTC)Reply

• Note: I have changed the target of the merger proposal to Compass rose - see the new discussion at Talk:Compass_rose#Merger_proposal. RockMagnetist(talk) 07:36, 8 November 2015 (UTC)Reply

@Rockscientist. I am afraid I am not seeing the point of these merger proposals. Why so eager to get rid of this article? Seems fine by itself, it can be connected from many other articles. Walrasiad (talk) 09:05, 8 November 2015 (UTC)Reply

@Rockscientist. excuse my imperfections I've rewritten the Use of rhumblines as you've demanded.--Mcapdevila (talk) 17:48, 9 November 2015 (UTC)Reply

Thanks, Mcapdevila. I have decided to drop the whole merge idea. RockMagnetist(talk) 18:09, 9 November 2015 (UTC)Reply

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Dear all

I have discussed this article with a group of experts on portolan charts, and the consensus is that it needs much improvement in scope and in content. I have volunteered to make improvements to the article and, to begin, I have drafted a table of contents that I copy below. Please let me know if anyone opposes this new outline and, if it is not the case, I will start editing the article next weekend.

1. Definition
2. Contents
   • rhumb lines, coasts and islands, toponyms, flags, city views...
3. Production
   • data compilation, drafting, copying...
   • production centers, prominent authors / schools
4. Use
5. Theories about their origin
6. Evolution
   • Expansion of coverage area
   • Latitude charts
   • Nautical planispheres

--Hispalois (talk) 16:38, 17 November 2018 (UTC)Reply

This article was the subject of a Wiki Education Foundation–supported course assignment, between 25 August 2025 and 19 December 2025. Further details are available on the course page. Student editor(s): Caccuk, Okapine (article contribs). Peer reviewers: MizzMandaPanda, WyattD04.

— Assignment last updated by K8shep (talk) 14:54, 30 October 2025 (UTC)Reply

Hello, I am going to be working on adding to the "specific features" section to add information I've found on the use of symbols for navigational hazards. Okapine (talk) 16:43, 17 October 2025 (UTC)Reply

I'm going to add a sentence on the early method of creation of the charts to the "theories of origins" section. Caccuk (talk) 16:44, 17 October 2025 (UTC)Reply

I'm going to add some information to the "theories of origins" section, specifically about other ideas not already mentioned, and a little bit of information to the "use" section.Caccuk (talk) 14:10, 14 November 2025 (UTC)Reply

I am going to add more information on the various symbols for navigational hazards to the "Symbols" section I started.Okapine (talk) 17:23, 14 November 2025 (UTC)Reply

I am going to add more information to the use and evolution sections Caccuk (talk) 17:44, 21 November 2025 (UTC)Reply

I'm going to add more info to the section I started on symbols.Okapine (talk) 04:09, 9 December 2025 (UTC)Reply

I'm going to add some information to the production section.Okapine (talk) 06:20, 11 December 2025 (UTC)Reply

I'm going to add some information I found to the Use section. Okapine (talk) 06:27, 12 December 2025 (UTC)Reply

While there have been many hypotheses about their origin, including creation by neolithic, Greek, Roman, and Egyptian civilizations, scholarly consensus has coalesced around two. Still others have suggested that given the adornment and ownership records of many of the charts, they may not have even served a practical navigational role. However, there are two principal scholarly hypotheses concerning their origin: the mediaeval origins hypothesis and the pre-medieval origins hypothesis.

The idea that scholarly consensus has coalesced around two is repeated twice. Fine; delete one. But: All of neolithic, Greek, Roman, and Egyptian are “pre-medieval”, so it’s nonsensical to distinguish “pre-medieval” from these various hypotheses. It’s also nonsensical to even say that scholarly consensus has has coalesced around those two: there aren’t any other explanations. No coalescing, or even commentary, needed about that. It’s useful to distinguish between medieval and various pre-medieval hypotheses, but nonsensical to group all the pre-medieval into one in this way. Just seems like jumbled snippets from the sources. I’ll fix this if no one closer to the topic does. Strebe (talk) 19:45, 14 November 2025 (UTC)Reply

Thank you for your feedback. I see what you mean about the wording of this section, and am currently working on improving it to make more sense. Caccuk (talk) 16:19, 1 December 2025 (UTC)Reply