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Muslim surveyors invented triangulation, but used the square and plumb line of the Romans.

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Muslim surveyors invented triangulation, but used the square and plumb line of the Romans.

Al-Khwarizmi (780 – 850) added to the Greek-invented astrolabe the shadow square (which used the angle and the distance to calculate the height of a hill).

Al-Biruni’s plumb line, square, angle-measuring devices, and trigonometry were similar to those used in the first century BC by Roman surveyors mapping the city of Rome.

Although primitive triangulation had been used in pre-Islamic times to measure the height of hills, Maslama al-Majriti and ibn al-Saffar working together, were the first to use triangles and trigonometry to do land surveying.
Surveyors using triangulation could determine relative longitude for the locations within a triangulation network.

Abū Rayhān al-Bīrūnī (973 – 1048) was born a Shiite, but “his religion was tempered with agnostic tendencies”.

He expanded upon the trigonometry and triangulation land surveying methods invented around the year 1000 in Muslim Spain by Maslama al-Majriti and ibn al-Saffar. Al-Biruni’s innovation was to create triangulation networks (systems of very large triangles). He divided an area into triangles and then used  trigonometry to determine the direction and the “as the crow flies“ distance between cities. The relative latitude and longitude could be calculated for locations that were part of that network of triangles.
The British later used the same method, but in 3 dimensions, when they mapped the Himalaya Mountains in the 19th century.

Image by Paul N. Hasluck, via Wikimedia Commons.
image credit–plumb_square.png

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