Marinus of Tyre

Marinus of Tyre (Greek: Μαρῖνος ὁ Τύριος, Marînos o Týrios; c. AD 70–130) was a Greek or Hellenized geographer, cartographer and mathematician, who founded mathematical geography and provided the underpinnings of Claudius Ptolemy's influential Geography.

Marinus was originally from Tyre in the Roman province of Syria. He and his work were a precursor to that of the great geographer Claudius Ptolemy, who used Marinus's work as a source for his Geography and acknowledges his great obligations to him. Ptolemy said, "Marinus says of the merchant class generally that they are only intent on their business, and have little interest in exploration, and that often through their love of boasting they magnify distances." Later, Marinos was also cited by the Arab geographer al-Masʿūdī. Beyond this, little is known of his life.

Marinus's geographical treatise is lost and known only from Ptolemy's remarks. He introduced improvements to the construction of maps and developed a system of nautical charts. His chief legacy is that he first assigned to each place a proper latitude and longitude. His zero meridian ran through the westernmost land known to him, the Isles of the Blessed around the location of the Canary or Cape Verde Islands. He used the parallel of Rhodes for measurements of latitude. Ptolemy mentions several revisions of Marinus's geographical work, which is often dated to AD 114 although this is uncertain. Marinus estimated a length of 180,000 stadia for the equator, roughly corresponding to a circumference of the Earth of 33,300 km, about 17% less than the actual value.

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