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The map of Ahmed ibn Sahl al-Balkhi showed the Indian Ocean as connected to the Pacific Ocean.
A map of al-Biruni showed Spain being a short distance from China.
Abū al-Wafā’ Būzjānī calculated the difference in longitude between Baghdad and an observatory in what is now Uzbekistan, by comparing the angles to the same eclipse of the moon.
The sea captain Ahmad Ibn Mājid devised a route from India to Malaysia.
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The map of Ahmed ibn Sahl al-Balkhi (850 – 934) showed the Indian Ocean as connected to the Pacific Ocean.
In 870, “The Book of Roads and Kingdoms“ by the Persian geographer Ibn Khordadbeh (820 – 912) mapped the trade routes within the 9th century Muslim world and to China, Japan and Korea, and gave the history of Persia.
Al-Biruni (973-1048) was way off in his calculations of antipodes (cities on the opposite side of the earth), and his map showed Spain being a short distance from China.
Abū al-Wafā’ Būzjānī in the 10th century calculated the difference in longitude between Baghdad and an observatory in what is now Uzbekistan, by comparing the angles to the same eclipse of the moon.
12TH CENTURY WORLD MAP
In 1154, the Arab geographer Muhammad al-Idrisi (1099 – 1161) created a world map (with south at the top) including all the Muslim-occupied lands from Spain to India and maybe China.
14TH CENTURY MAPS
In the early 14th century, Ismail Abu’l Fida [Abulfeda] wrote a geographic work titled “The true position of the countries”. I presume he was an Ismaili (Shia Sevener).
He gave the latitude and longitude of Quanzhou China.
Although there is no record of it, I assume Abu’l Fida used a marine sandglass to keep accurate time on the ship he sailed on to China.
There is no claim he used longitude to navigate the ship at sea, so I assume he used an astrolabe that was only accurate for use on land.
15TH CENTURY AFRICA TO MALAYSIA ROUTE
The sea captain Ahmad Ibn Mājid (1421 – 1500?) devised a route from India to Malaysia that would be followed by later navigators. About 50 years after he died, a legend was invented that while Ahmad Ibn Mājid was drunk, he gave to Vasco da Gama a secret map of the route from Africa to India.
Image of Al-Idrisi map of 1154 is shown rotated 180 degrees (Al-Idrisi had south at the top), via Wikimedia Commons.
image credit https://en.wikipedia.org/wiki/File:TabulaRogeriana_upside-down.jpg