# Did Ancient Maritime Navigation Techniques Presume A Round Earth?

**URL:** <https://boards.straightdope.com/t/did-ancient-maritime-navigation-techniques-presume-a-round-earth/994447>\
**Category:** Factual Questions\
**Created:** [December 11, 2023, 9:24pm UTC](https://boards.straightdope.com/t/did-ancient-maritime-navigation-techniques-presume-a-round-earth/994447 "2023-12-11T21:24:26Z")\
**Posts on this page:** 3\
**Page:** 4

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**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\
**Post date:** [December 16, 2023, 5:32pm UTC](https://boards.straightdope.com/t/did-ancient-maritime-navigation-techniques-presume-a-round-earth/994447/61 "2023-12-16T17:32:39Z")

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Johannes Werner published some lunar distance stuff in 1524, so Columbus would not have had access to that. He is known to have carried at least this

> **[Calendarium and ephemerides : Regiomontanus, Joannes, 1436-1476 : Free...](https://archive.org/details/ljs300/mode/2up)**
>
> Kislak Center for Special Collections, Rare Books and Manuscripts, LJS 300. Lambach?, Austria, 1500. Manuscript copy of the Calendarium and Ephemerides as...

which has lunar positions (however with occasional errors of a degree or more!!) but it does not matter since with that particular method you need pretty accurate angular measurement, like less than a minute; if we are talking on the order of half a degree then you may as well not even bother.

This article

> **[Columbus's Method of Determining Longitude: An Analytical View | The Journal...](https://www.cambridge.org/core/journals/journal-of-navigation/article/abs/columbuss-method-of-determining-longitude-an-analytical-view/C18AA671D09A1FE8504F5D627CDFAA79)**
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> Columbus's Method of Determining Longitude: An Analytical View - Volume 49 Issue 1

claims Columbus obtained “not even bother” accuracy when he tried observing a lunar eclipse on 14 September 1494 and one on 29 February 1504, and makes the argument that Columbus did not use lunar-planetary conjunctions with any success to determine longitude.

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**Author:** ![3AxisCtrl](https://avatars.discourse-cdn.com/v4/letter/3/ecd19e/32.png) [@3AxisCtrl](https://boards.straightdope.com/u/3AxisCtrl)\
**Post date:** [December 18, 2023, 1:31pm UTC](https://boards.straightdope.com/t/did-ancient-maritime-navigation-techniques-presume-a-round-earth/994447/62 "2023-12-18T13:31:38Z")

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> [@Machine\_Elf](#):
>
> The earth is 25,000 miles in diameter.

Circumference?

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**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\
**Post date:** [December 18, 2023, 1:58pm UTC](https://boards.straightdope.com/t/did-ancient-maritime-navigation-techniques-presume-a-round-earth/994447/63 "2023-12-18T13:58:37Z")

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> [@3AxisCtrl](#):
>
> Circumference?

Meh, I like to think of the world as a big place.

(but you’re factually correct - 25K miles in circumference.)

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