Camara

With the latitudes of two points measured, you know the angle of your path, and with the distance between them you can despict them in a map. Arab navigators had instruments to measure latitudes so they can solve the problem. The book I refer has Marco Polo's indicated distances, even as estimates I don't believe an error of half of Earth would be possible. When Vasco da Gama arrives at Melinde, the king offers him a map of the Indian ocean. Arab navigators knew well the distances to Malacca, and navigated to Tidore and Ternate as well. But you still miss half of the world to reach Azores, that is not a small error, that is a gigantic error. IIRC (just by mind, not sure) Ptolomaic map despict roughly 180 degrees of the world, missing another 180 - the pacific and americas.

Problem here. Traditional theory says that this was his belief (I don't believe, see the information he had) and this portuguese theory says he wanted Castile to claim the Caribbean (showing some inaccurate information, maybe maps like this one), so this map does not proves nothing. BTW when was this map drawn?

I don't think arab cartography would make such an error. Nor anyone. Eurasia size was known, see below.

What?? Portugal spent an entire century navigating everywhere (west - some voyages, south - main voyages, north - luso-danish secret expeditions), when the India objective is set the main though is around Africa. Why? Because it is much closer! If Portugal rejected Columbus (if...) and Toscanelli is because Portugal knew west was not the closest way to India. Portugal did some voyages to west, like Teive in 1452 (I think he reached Bermuda, personal opinion), Portugal kept an open minded exploration but the India issue was concentrated in the south of Africa. Portugal did not need Columbus nor Vespucci to show anything.
If Portugal really believed Columbus hit India everything would be different. Columbus' Indies would be portuguese by Alcáçovas anyway, as they are south of Canary Islands. The alternative would be war, which castille wanted to avoid at any means.
Portugal only "explores" (to me the real word is "officializes") america after Vasco da Gama's return: Lavrador and Barcelos quickly go to Greenland (1499) (I don't think they went to today's Labrador, anyway their cartography of Greenland would be the best for like 300 years, see Cantino 1502) and Cabral "accidentaly" discovers Brazil (1500). BTW Cabral said Brazil was a new land, so he predates Vespucci on that. Nova's voyage was not exploration, his voyage was to get to India (second voyage), in the return he discovered St Helena, I'm not sure of Ascension.

With another basic tool, latitude, you know everything. They had it.

I don't have them here. By mind I remember Pacheco Pereira's data (1500's, his book Esmeraldo de Situ Orbis), which calculates with precision (4% error), I'm not sure, the distance of one degree of meridian, with that the calculation of the size of Earth is trivial. I know it is a decade later, but an error of such magnitude is ridiculous for just a decade before. But looking at the data they had, it is almost impossible they got the radius wrong. Do you agree that they knew the size of the world?

[Benhaim worked in Portugal, Toscanelli don't. I think you're underestimating portuguese secrecy in John II's time. People died if they spoke too much. We do not even have Dias' explanation of his voyage, why do you think we would have the portuguese view of the world? AFAIK from this period we only have Zacuto's work (only because John II gave them to Columbus, they were super secret) and nothing more. Or do you believe Portugal did nothing in this period?]

Do you believe the size of Eurasia was not known? Look for example at Ptolomy's world map. Asia is twice as big as the Mediterranean, like today's maps. They knew the distances right. As I write this post I found out what I was looking for: Ptolomy's map shows only 180 degrees of the world! With Eurasia included. See on botton of the map: http://upload.wikimedia.org/wikipedi...-_Ulm_1482.png

When I have the book I will quote Polo's distances because they may also show the missing half. But Covilhã probably had better information.

Do you agree with me that right world size and right known world size Portugal or anyone with a small piece of mathematical brain could easily figure out that there was half of the world that was unknown?

Atlantid

The following should be of interest. There are articles of a possible Potuguese connection. Click the link to find more articles.
__________________________________________________ ________________

Seeking Columbus’s Origins, With a Swab

BARCELONA, Spain — When schoolchildren turn to the chapter on Christopher Columbus’s humble origins as the son of a weaver in Genoa, they are not generally told that he might instead have been born out of wedlock to a Portuguese prince. Or that he might have been a Jew whose parents converted to escape the Spanish Inquisition. Or a rebel in the medieval kingdom of Catalonia.

Yet with little evidence to support them, multiple theories of Columbus’s early years have long found devoted proponents among those who would claim alternative bragging rights to the explorer. And now, five centuries after he opened the door to the New World, Columbus’s revisionist biographers have found a new hope for vindication.
The Age of Discovery has discovered DNA.
In 2004, a Spanish geneticist, Dr. Jose A. Lorente, extracted genetic material from a cache of Columbus’s bones in Seville to settle a dispute about where he was buried. Ever since, he has been beset by amateur historians, government officials and self-styled Columbus relatives of multiple nationalities clamoring for a genetic retelling of the standard textbook tale.
Even adherents of the Italian orthodoxy concede that little is known about the provenance of the Great Navigator, who seems to have purposely obscured his past. But contenders for his legacy have no compunction about prospecting for his secrets in the cells he took to his grave. And the arrival on Oct. 8 of another anniversary of Columbus’s first landfall in the Bahamas has only sharpened their appetite for a genetic verdict, preferably in their own favor.
A Genoese Cristoforo Colombo almost certainly did exist. Archives record his birth and early life. But there is little to tie that man to the one who crossed the Atlantic in 1492. Snippets from Columbus’s life point all around the southern European coast. He kept books in Catalan and his handwriting has, according to some, a Catalonian flair. He married a Portuguese noblewoman. He wrote in Castilian. He decorated his letters with a Hebrew cartouche.
Since it seems now that the best bet for deducing Columbus’s true hometown is to look for a genetic match in places where he might have lived, hundreds of Spaniards, Italians, and even a few Frenchmen have happily swabbed their cheeks to supply cells for comparison.
“You would be proud to know that the man that goes to America the first time was Catalan,” said Jordi Colom, 51, an executive at a local television station whose saliva sample will help test the contention that Columbus was born in Catalonia, the once-independent eastern region of modern Spain that still fosters its own language, culture and designs on independence.
No chance, said Renato Colombo, 62, a retired Italian engineer who proffered his DNA to reassert his nation’s hold on the status quo. “It has never been in doubt that he was from Liguria,” the region in northwest Italy of which Genoa is the capital, he insisted. “In his personality, there are the characteristics of the Genoese, mostly represented by his project and his visceral attachment to money and his determination.”
Mr. Colom and Mr. Colombo are both “Columbus” in their native tongues. And along with their names, each inherited from his father a Y chromosome — a sliver of DNA passed exclusively from father to son — which would have been virtually unchanged since the 15th century. A Columbus match to either man’s Y chromosome would tie him to that paternal line’s Italian or Catalonian home.
“What I want to write is the final book on Columbus, and I will not be able to do it without science to settle this,” said Francesc Albardaner, who was seduced by the possibility that DNA — a tool whose answers are treated as indisputable fact in courtrooms and on TV shows — would endorse his deeply held belief in the Catalonian Columbus.
Mr. Albardaner, a Barcelona architect, took more than three months off work, called 2,000 Coloms and persuaded 225 of them to scrape their cheeks at his Center for Columbus Studies in Barcelona. The swabs along with 100 Colombos collected in Italy are being analyzed by Dr. Lorente at the University of Granada and scientists in Rome.
A Colom match could overturn conventional wisdom about the nationality, class, religion, and motives of the man who began the age of American colonization. On the other hand, an association with Colombo DNA would cement Italy’s national pride in a man who remains a hero to many, complaints from American Indians he slaughtered, Africans he enslaved and Vikings who got there first notwithstanding.
But some petitioners think it is a waste of time to scour the phone book for Columbus’s long-lost kin. Insisting that they know who Columbus’s father really was, they are asking Dr. Lorente to perform a 500-year postdated paternity test. The government council president of Majorca, for instance, has paid him to examine the exhumed remains of Prince Carlos of Viana, the one-time heir to the Catalonian crown who reportedly fathered a son with a woman on the island whose last name was Colom.
The vials of royal DNA in Dr. Lorente’s freezer also include contributions from two living members of the now deposed Portuguese royal line: those of the Duke of Bragança and the Count of Ribeira Grande who argue that Columbus was a member of their family — the product of an extramarital affair involving a Portuguese prince.
“This is the true story, forget the Italians, forget the Spanish,” said Count Jose Ribeira, 47, a real estate developer in Lisbon who attended the dedication of a new Columbus monument last year in the Portuguese town of Cuba that claims to be Columbus’s birthplace. If it is, all three samples should contain the same Portuguese genetic imprint.
But this year, anyway, the Columbus Day parade in New York will feature Maserati sports cars, flag throwers from Siena and Lidia Bastianich, the Italian cooking show host, as grand marshal.
Those who had hoped DNA would crash the Italian party expected a genetic pronouncement from the scientists on the 500th anniversary of Columbus’s death last May. Or last Columbus Day. Surely by this one. After all those centuries in a crypt, however, a mere trace of DNA was all that could be extracted from Columbus’s bones, and Dr. Lorente has said he is loath to use it indiscriminately.
To make things even tougher, he has found that Catalonian Coloms and Genoese Colombos are so closely related it is hard to distinguish them with the standard Y-chromosome tests. So he is searching for more subtle differences that would allow him to link Columbus to a single lineage.
“My heart,” Mr. Albardaner said, “will not endure so many delays.”
Others have accused Dr. Lorente of nationalist bias, of covering up results that suggest Columbus was a Jew and of withholding a historical treasure from the Western world.
“Will Lorente continue to hide what the scientists know concerning Columbus’s DNA?” asked Peter Dickson, a retired C.I.A. analyst whose self-published book on Columbus argues that he was part French, part Italian, part Spanish and part Jewish, in an e-mail message to fellow Columbus buffs. “Will he remain silent on Columbus Day once again?”
Dr. Lorente says he will. And in the absence of data, rumors are flying.
Olga Rickards, a Lorente collaborator at Tor Vergata University in Rome, has been quoted as saying that she “wouldn’t bet on Columbus being Spanish.” A graduate student of Dr. Lorente’s who had studied the Colombo DNA led Italian newspapers to believe Columbus was from Lombardy, north of Genoa, although she had apparently never seen Columbus’s DNA. And Nito Verdera, a journalist from the Balearic island of Ibiza, who says the explorer was a Catalan-speaking Ibizan crypto-Jew, cited leaks from Dr. Lorente’s team that link Columbus to North Africa.
“I’m very sorry about the great expectation among some historians that they all want the DNA to confirm their hypothesis,” Dr. Lorente said. “But science needs its time and has its pace.”
If Columbus was an adopted name, as some scholars believe, tests of Coloms and Colombos will have been in vain. Moreover, with dozens of generations separating all those Coloms, Colombos, princes and counts from Columbus’s time, a long-hidden adulterous liaison could have severed the Y-chromosome-and-surname link.
Even with a match questions will remain. What if Coloms moved to Genoa or Colombos to Barcelona? Today’s distinct regional identities may not be reflected in the genetic code of the earlier era.
Mr. Albardaner still brings Columbus novices to the Historic Archive of Protocols in Barcelona, where they can hold a yellowed note from the 15th century filled with the calligraphic scrawl of the man he believes stumbled upon the Caribbean while looking for a western route to India.
He is less sure now that there will be a precise answer to who Columbus was or where he was from, but he is still hoping it will come from the DNA.
“Maybe it will say he’s from Catalonia. Maybe it will be a complete lockout. Maybe we find his DNA is completely dissimilar to any known DNA, he comes from Mars, well, perfect, O.K.”
“Then,” he said, “I stop.”
http://www.historum.com/newreply.php...uote=1&p=52259

Edgewaters

Actually no, you don't know your angle - that's part of the problem. With latitude you only know your position and only in one dimension. A compass helps, but unless you're stopping every few hundred yards and doing all your bearings and calculations each time, you can't make an accurate depiction. You're don't seem to understand how maps were made in that period: their accuracy depended entirely on the level of familiarity of the nautical community with the area in question. That's why England and the Baltic countries look all screwed up on the Iberian maps, because they weren't as familiar with those areas. The only area that's anything close to precise is the Meditteranean, and that's because the nautical traditions go back a few thousand years ...

To do a precise survey takes an enormous amount of time. The first precise survey of even a small European country - Great Britain - wasn't started until the late 1700s and it wasn't finished for 70 years. Before that, the shapes of coastlines and islands was a matter of educated guesswork - the more educated and familiar they were, the more accurate they were. The first thing you'll notice about all the old maps is that the further away you get from the place the map was made, the more distortions and inaccuracies there are - because they didn't have the same level of familiarity. To get anywhere across the open sea they didn't use a world map ... they used a course plot.

No, not because they thought it was shorter, because it was a proven route. They knew that from the Muslims. All you had to do was follow the coast. But they were still seeking a western passage.

I detect a whiff of nationalist revisionism and fantasizing here. You're Portuguese aren't you?

Yes, let's have a look at that, shall we? That's the best knowledge Portugal had, one of their secret maps that got stolen. Here it is:



Notice that the coastline of the Far East is totally distorted, and Eurasia is massive, about six times the length of the Meditteranean ... so much for the idea that they secretly knew that the actual distances involved. They didn't, as this demonstrates, nor had they any accurate idea about the size or shape of the Far East. Even Africa is pretty screwed up ... it looks alright at first glance, until you realize that according to the map, the Suez Canal would have to cross land further than the distance between Gibraltar and Normandy. So much for the super-duper Portuguese cartographers knowing the exact sizes of the landmasses. Their maps were heavily distorted and, contrary to popular conception, were NOT used for precise navigation, but just to get very general ideas about where things lay. Pilots travelling a known route in the open sea, away from the coastline, used course plots described to them by other pilots who had travelled the route.

So did Cabot (1497) but that's not the point, they didn't know that the whole route west was blocked by a single landmass stretching from the Arctic to nearly the Antartic. Vespucci demonstrated that it was, indeed, one single large landmass.

No, you're confusing his 1501 voyage with his 1505 voyage. He made two separate trips, one west and one along the usual route (the coastline of Africa) ... he did not discover Ascension etc on his return, because as Commander of the Third Expedition to India, he was specifically charged to find a westerly route and set out west. The mission was a bust and he returned home, then set out again in 1505 around Africa.

I asked you for proof they had accurate measurements of the size and shape of the Far East and the East Indies, not that they knew the circumference of the Earth. This answer isn't acceptable because the size and shape of the globe are irrelevant until you know the size and shape of Eurasia and how far east it was to get to the East Indies.

No, its not. They hadn't had the time to do an accurate survey - it would have taken a century or more using astrolabes and compasses, and even if vast funds and time were expended trying to do it, it would be extremely unlikely to be fully accurate anytime before the sextant is developed. And even if somehow it was accurate, it couldn't be projected onto the globe accurately until the Mercator projection and Wright's equations for transferring a two-dimensional map onto it were developed. They didn't even have an accurate idea of the distance it would take to build the Suez Canal, and that was not that far away - just the other side of the Meditteranean. And you expect that they had a secret, accurate map of the entire Far East? Why do you think this? Where's the evidence?

Cantino stole one of their secret maps, and it doesn't show the kind of anachronistic map you're claiming they had. They were ahead, but to think they had anything even remotely as accurate as a modern map is absurd - they didn't have the technology.

Well, Ptolemy was alot more accurate than the Portuguese cartographers then. Look at Asia in the Cantino map, compared to the Meditteranean.

The secret maps of the Portuguese cartographers, according to the evidence, still had the coastline of Asia in about the same place as Toscanelli and Benheim, and the distance west to Cathay was still roughly the same.

I don't need a secondary source to tell me what Polo's journal says, because I've read it and you can too:

http://www.gutenberg.org/etext/10636

http://www.gutenberg.org/etext/12410

If you could get an accurate map of Eurasia out of that, I'd be most impressed. It reads like an adventure novel, not a geographic account. He rarely gives any distances or positions at all, and most of them are wholly vague and imprecise (and even then, usually inaccurate). This is an example of the how the Polo text gives distances, when it does:

"When you have left the city of Changan and have travelled for three days through a splendid country, passing a number of towns and villages, you arrive at the most noble city of Kinsay"

Three days - whether by horse or foot, and in what direction, he doesn't say. Good luck making a precision modern map out of that.

Camara

What?
If you know the latitudes of two points and the path length between them you can know the difference in longitudes, with that you know their position in a sphere. You don't need to, but with this you can calculate the angle.
Another way is to navigate/walk/whatever with a constant latitude, so you can easily figure out longitude diference.

Ptolomy had longitudes in his map (compare with today's values, his 180 degrees for eurasia is just more 30 degrees than reality). It is true that most of the maps of the time had an enlarged Eurasia, bigger than Ptolomy, but that is mainly in post-India part (Eurocentrism...). There was no way anyone with information though India was closer by west, because if you shrink the pacific you have to grow indonesia and malay-siam, but India's distance to Europe was known so the distance to get there was the same.
I'm not saying they though Asia was closer by east, I'm saying they knew India was closer by east. Of course Asia could had an unknown big extension as a chain of islands so that it was just a short distance to them from Europe, but India would still be far away in the west path...
(But I believe arab navigators knew the distances to Indonesia right, but this is my opinion and I do not have references for that, maybe I have to research because I don't know if this is true or not.)

Of course. But if you join an iberian and an arab map you will get a more accurate one in Iberia and Arabia. As baltic people and english weren't as active in cartography as Portugal and Portugal did not go there to measure there was no accurate map of those lands. But arabs were interested in cartography.

Of course.

A proven route with a possible locked Africa? Portugal kept open minded because of this possibility. Toscanelli proposed navigation through west in 1474 but Portugal wasn't interested, although Portugal had the ships and navigation tools to do those voyages. Do you think that if Portugal believed India was closer by west they would not try it? They would instead do a longer and more dangerous voyage around Africa? The east route had the problem of navigation in the core of the arab waters, enemies of Portugal. The west route would minimize this problem.

I really can't believe you're saying this. Columbus (at least before 1484) and Vespucci both worked for Portugal just like Gama, Lavrador, Cabral, etc, so I don't see how can you use that as an argument of my hypotethical though of "portuguese nationalism". You completely misunderstood my sentence. I did not say that Columbus and Vespucci had nothing to show to Portugal just because they worked for Castile/not-Portugal (nationalistic thoughts), as you know they also worked for Portugal (and the theory I'm presenting actually says Columbus is portuguese!) so this becomes void. The Portuguese exploration masters were not the navigators only, but also the cartographers and mathematicians that worked in the shadows. I think that people like Abraham Zacuto had nothing to learn from people like Columbus or Vespucci or Cabral or Gama as he was a master. And Portugal had some people like him in John II's group. What could Columbus or Vespucci or Cabral or Gama teach to these guys? Of course provide some data and navigation tricks but elaborated intelectual discussions as the size of Earth, longitudes and latitudes calculus, charts' interpretation and elaboration? Note that Columbus is the most intelligent of these guys (that's also why I do not believe he believed in "his view of the world"), and Cabral and Gama from what I know knew only the minimum necessary to be the captains of their armadas. But what could Columbus and Vespucci teach to this portuguese mathematician group (with an ex-castilian jew, a bohemiam,... (not many portuguese to my "nationalistic group"...))? Cabral and Gama surely were worse.
Yes I'm portuguese but I could as easily be an alien.

Oh really? I agree it was the best portuguese map for north america as it shows Corte-Real and Lavrador & Barcelos voyages (Cantino actually talks about the voyage of Corte-Real). But the best map Portugal had? Who said that? And based on what? Portugal actually distorted maps to confuse foreigners, and I have a reference for this from a person of those times, but unfortunately I can't give it now.

Six times? I count three (from Israel to China) at max. Anyway whatever, look at India, it is one "mediterranean" away from Israel. So it doesn't matter how big post-India Asia will be, as India will be closer east.

Remember what I said about the shapes? Now look to the map. Aren't Africa, India, even ridiculously wrong Malaysia/Sumatra/Java/, Newfoundland, Greenland in the right places in latitude and "longitudinal distance from Europe"? This map is 1502, Portugal only went to Calicut and Cochim, of course Portugal did not know the exact shapes of Malaysia nor Persian Gulf, Portugal never went there. But the cartography of the coasts that Portugal analysed is good, or you don't agree with this?
As for the Suez, look at Martellus, Ptolomy, Covilhã voyage,... one question, do you believe this Suez was the one the best portuguese cartographers believed? I'll give you one example. Look at Greenland in Cantino, after Lavrador & Barcelos 1499-1500:

Cantino 1502 thing, Newfoundland (or probably Newfoundland+part of Labrador combo) and Greenland, look at the polar circle for orientation


See how good it is, specially the west coast? Now look at the other portuguese maps that show Greenland, specially the ones with the north-american portuguese possessions, here are some examples:

Reinel 1504 (there is debate about the date of this one)
http://upload.wikimedia.org/wikipedi..._munich_00.jpg
I removed it from the post as it was too big for the forum.

Lasso 1575


Where is the beatiful and accurate Greenland, specially its west coast? How do you explain this? With lost information? Now imagine Cantino didn't succeed in steal "his" map. How would we know that Labrador & Barcelos did that work in Greenland? For example how do you explain Pigaffetta's saying that Magellan saw the strait of Magellan in portuguese secret maps before he went there? Portugal had secrecy in the discoveries (that doesn't mean we can now claim everything and claim it was secret so that's why we never heard of it, that's silly and unscientific) so it makes things much more complicated to research.

Camara

Cabot did not think it was a part of Asia, the land of the Great Khan (I ask)?

In 1502 he went to India, and in the return he discovered St Helena, I read that in Barros' Decadas da Ásia. What do you mean with westerly route? Are you talking about the return from India?

This information was just to show the size of Earth was known.

I was talking about the size of Earth, it was known to some precision. I did not say Portugal had a secret and accurate map of the Far East, I said Portugal had an estimative of the position of the Far East, for example, from Ptolomy.
I did not say Portugal had an accurate map of the world! I said Portugal could conclude from Ptolomy's map and from the size of Earth that the unknown part of the world would be big. There's no uber map in my thoughts!

I don't see the uber Asia in Cantino, it is about the same in proportions as todays maps - Israel to China. Doesn't that mean that its distances were known, at least in comparison with Europe? Portuguese cartographers had to rely on Ptolomy etc because they never went there, I don't see where's the problem if their sources were actually worse than Ptolomy's map itself without contradicting data inside the range of calculation/measurement/assumption errors. If Portugal made his world view based on the Ptolomy's map and the size of Earth, then it was very accurate as Ptolomy gives 180 degrees from Canary Islands to Far East. It is possible that later they changed the idea (to a worse one), but maybe only some time after the Columbus proposal/voyage. I don't think so, but that is possible. This theory says Portugal knew India was closer east and likely that Portugal knew the caribbean, so Columbus mission was to make Castile believe India was closer west. If Toscanelli believed in that why wouldn't the kings of Castile? Actually castilian cartographers did not believed in Columbus. But the traditional theory also says Columbus believed in a smaller world, IIRC.
There is one muslim globe I think, I would like to see it.

Again, I'm not saying Portugal knew the exact shape of the world, just the enough to figure out India is closer east than west. And there is no longitude in Cantino to compare.

I only referred Polo's distances as this Columbus' book mentions it, with values.

franco

it depends if you think of in Italy in its modern sense.