Editing History of Portugal (1415–1578) (section)

===Portuguese nautical science===
{{further|Portuguese Renaissance}}

The successive expeditions and experience of the pilots led to a fairly rapid evolution of Portuguese nautical science, creating an elite of [[astronomers]], [[navigators]], [[mathematicians]] and [[cartographers]], among them stood [[Pedro Nunes]] with studies on how to determine the latitudes by the stars and [[João de Castro]].

==== Ships ====
[[Image:Caravel Boa Esperanca Portugal.jpg|thumb|A modern replica of a Portuguese [[caravel]]]]

Until the 15th century, the Portuguese were limited to coastal [[cabotage]] navigation using [[barque]]s and ''barinels'' (ancient cargo vessels used in the [[Mediterranean]]). These boats were small and fragile, with only one mast with a fixed quadrangular [[sails|sail]] and did not have the capabilities to overcome the navigational difficulties associated with Southward oceanic exploration, as the strong [[wind]]s, [[shoal]]s and strong [[ocean current]]s easily overwhelmed their abilities. They are associated with the earliest discoveries, such as the [[Madeira]] Islands, the [[Azores]], the [[Canary Islands|Canaries]], and to the early exploration of the north west African coast as far south as [[Arguim]] in the current [[Mauritania]].

The ship that truly launched the first phase of the Portuguese discoveries along the African coast was the [[caravel]], a development based on existing fishing boats. They were agile and easier to navigate, with a tonnage of 50 to 160 tons and 1 to 3 masts, with lateen triangular sails allowing [[luffing]]. The caravel benefited from a greater capacity to [[tack (sailing)|tack]]. The limited capacity for cargo and crew were their main drawbacks, but did not hinder its success. Limited crew and cargo space was acceptable, initially, because as exploratory ships, their "cargo" was what was in the explorer's feedback of a new territory, which only took up the space of one person.<ref>[[Roger C. Smith (author)|Roger Smith]], "Vanguard of the Empire", Oxford University Press, 1993, p.30</ref> Among the famous caravels are ''Berrio'' and ''Caravela Annunciation''.

With the start of long oceanic [[sailing]] also large ships developed. "Nau" was the Portuguese archaic synonym for any large ship, primarily [[merchant ship]]s. Due to the [[piracy]] that plagued the coasts, they began to be used in the [[navy]] and were provided with cannon windows, which led to the classification of "naus" according to the power of its artillery. They were also adapted to the increasing maritime trade: from 200 tons capacity in the 15th century to 500, they become impressive in the 16th century, having usually two [[deck (ship)|deck]]s, [[stern]] castles fore and aft, two to four masts with overlapping sails. In India travels in the sixteenth century there were also used [[carrack]]s, large merchant ships with a high edge and three masts with square sails, that reached 2000 tons.

==== Celestial navigation ====
[[File:AlmanachPerpetuum.jpg|thumb|right|200px|[[Ephemeris]] by [[Abraham Zacuto]] in Almanach Perpetuum, 1496]]
In the thirteenth century [[celestial navigation]] was already known, guided by the sun position. For celestial navigation the Portuguese, like other Europeans, used [[Arab]] navigation tools, like the [[astrolabe]] and [[Quadrant (instrument)|quadrant]], which they made easier and simpler. They also created the [[cross-staff]], or ''cane of Jacob'', for measuring at sea the height of the sun and other stars. The [[Southern Cross]] become a reference upon arrival at the Southern hemisphere by [[João de Santarém]] and [[Pedro Escobar]] in 1471, starting the celestial navigation on this constellation. But the results varied throughout the year, which required corrections.

To this the Portuguese used the astronomical tables ([[Ephemeris]]), precious tools for oceanic navigation, which have experienced a remarkable diffusion in the fifteenth century. These tables revolutionized navigation, allowing to calculate [[latitude]]. The tables of the Almanach Perpetuum, by astronomer [[Abraham Zacuto]], published in [[Leiria]] in 1496, were used along with its improved astrolabe, by [[Vasco da Gama]] and [[Pedro Álvares Cabral]].

====Sailing techniques====
[[Image:Oceanic gyres.png|thumb|200px|left|Map of the five major [[oceanic gyre]]s]]
Besides coastal exploration, Portuguese also made trips off in the ocean to gather [[meteorological]] and [[oceanographic]] information (in these were discovered the archipelagos of Madeira and the Azores, and [[Sargasso Sea]]). The knowledge of [[wind]] patterns and [[ocean current|currents]], the [[trade winds]] and the [[oceanic gyre]]s in the Atlantic, and the determination of latitude led to the discovery of the best ocean route back from Africa: crossing the Central Atlantic to the latitude of the Azores, using the permanent favorable winds and currents that spin clockwise in the Northern Hemisphere because of [[atmospheric circulation]] and the effect of [[Coriolis effect|Coriolis]], facilitating the way to Lisbon and thus enabling the Portuguese venturing increasingly farther from shore, the maneuver that became known as the ''"[[volta do mar]]"'' ({{langx|en|return of the sea}}).

====Cartography====
[[File:Fernão Vaz Dourado 1571-1.jpg|thumb|200px|right|Pre-mercator navigation chart of the Coast of Africa (1571), by Fernão Vaz Dourado (Torre do Tombo, Lisbon)]]
It is thought that [[Jehuda Cresques]], son of the Catalan cartographer Abraham Cresques have been one of the notable [[cartographers]] at the service of Prince Henry. However the oldest signed Portuguese sea chart is a [[Portolan chart|Portolan]] made by [[Pedro Reinel]] in 1485 representing the Western Europe and parts of Africa, reflecting the explorations made by [[Diogo Cão]]. Reinel was also author of the first nautical chart known with an indication of [[latitude]]s in 1504 and the first representation of a [[Wind rose]].

With his son, cartographer [[Jorge Reinel]] and [[Lopo Homem]], they participated in the making of the atlas known as "Lopo Homem-Reinés Atlas" or "[[Miller Atlas]]", in 1519. They were considered the best cartographers of their time, with Emperor Charles V wanting them to work for him. In 1517 King [[Manuel I of Portugal]] handed Lopo Homem a charter giving him the privilege to certify and amend all [[compass]] needles in vessels.

In the third phase of the former Portuguese nautical cartography, characterized by the abandonment of the influence of [[Ptolemy]]'s representation of the East and more accuracy in the representation of lands and continents, stands out [[Fernão Vaz Dourado]] (Goa ~ 1520 – ~ 1580), whose work has extraordinary quality and beauty, giving him a reputation as one of the best cartographers of the time. Many of his charts are large scale.