How the map was created
A while ago I started to be interested in the Expedition of Magellan and Elcano. The culprit, without him knowing it, was José Carlos G., author of the “History of Spain” podcast in memoriasdeuntambor.com, of which I am a fervent admirer.
The fantastic program that he dedicated to explain this expedition caused my interest in reading the original sources that have fortunately lasted to this day. And they are not few. I discovered then that the deck boatswain of the nao Trinidad, and later pilot of the Victoria, Francisco Albo, had written an extensive document in which he daily detailed his position, known as Derrotero de Francisco Albo, which I read.
Albo gives us day by day his latitude or "height" over the equator, that is, the degrees of separation to the equator, which he is able to find by taking the height of the sun above the horizon at noon. In addition to this, it indicates the course followed, and in many occasions also an estimate of the leagues covered in the day. However, in the 16th Century there was no means to determine the position by coordinates, since it was impossible to establish the longitude, that is, the left and right position on the map.
With all this, I was curious if I could find out the route followed in some sections of the trip. So I started using Google Maps for it, creating a marker per day, which I placed in the latitude that Albo said. Sometimes some data was confusing, but in general it seemed quite obvious to find the route by estimating the longitude, the only data we would need to make it more reliable.
Journey of Ferdinand Magellan to find a strait, from the cape of St. Agustin, by Francisco Albo, Virtual Library of the Spanish Ministry of Defence.
I had to find out which places corresponded to almost all the place names that he uses, for which I relied on old maps. In particular, the Theatrum Orbis Terrarum, published in 1570 by Abraham Ortelius, was very useful to me.
World map Theatrum Orbis Terrarum, year 1570.
After following their route by the Atlantic coast of South America, and seeing that it was not difficult, I encouraged myself to continue. At one point I could not stop anymore. Completing the route became a sort of obsession, and especially, the absolutely epic voyage of Elcano from Timor to the coast of where he could not stop, and the Cape Verde Islands where he had to flee in a hurry. In order to avoid the Portuguese, who dominated the routes around Africa, he went so far south that he was about to discover Australia, and he entered the fringe of the roaring forties, where nobody until then had sailed, in which the storms and currents still today pose a challenge for sailors. And all this without intending to stop at any time.
It was especially exciting to check the accuracy of the estimated position days after they passed the Cape of Good Hope. They were able to navigate the distance to Tenerife when they were still traveling across the Atlantic in front of Angola.
Once the route was completed, and seeing that on the Internet there was practically no map that was faithful to it, but were mostly mere outlines, I decided to make it public. Before doing so I had to spend a lot of time sorting the days chronologically. In addition, I incorporated all the position marks of the Derrotero, as well as from texts of Pigafetta or my own to complete the narration of what happened. Some problematic areas of the Derrotero I had to review dozens of times.
It was a long job, which served to review for the umpteenth time the positions I had established, and join them in their wooden ships.