A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: John Huth
Date: 2009 Nov 16, 16:56 -0500
Hi, All -
I attempted to do an analysis of the Marseilles tables. The first few paragraphs appear for those of you who would like an abstract of my conclusions. If you want a location by location analysis and the tables I derived, feel free to dive in.
As with any transcription, it's possible that I made significant errors. If you spot some, or have some ideas about the locations I couldn't identify or think I've made a wrong ID, I'd be interested to hear them.
Comparison of Marseilles Tables and Modern coordinates
Working with the Marseilles tables listed in John K. Wright’s 1923 paper, I tried to do a direct comparison with modern values. The first task was to find correlates with modern names. This was easy in some cases – e.g. Damascus, Roma, Jerusalem, Sanaa, etc. all have identical names. There are many cases where similar or ancient names and cognates appear – e.g. Barqah and Cyrene are comparables.
In some cases, there are marginal comparisons, in other cases, there are large areas that are difficult to pin down. E.g. “Gana” presumably represents the Empire of Ghana, but this is so large that it’s difficult to know which city or ruin of city to assign. Also, I chose to not use islands. I chose to reject islands, large regions (e.g. Ceylon, Gana), and sketchy comparisons. An example of a sketchy comparison is Emerita, which could be the ancient city of Augusta Emerita in Spain, but the latitude would place Emerita in the Bay of Biscay, very far from any cognate. Given the proximity to Corduba and Toledo, it seems surprising that it would be so far off, so I rejected this as a possible transcription error.
Having done this, I found that the latitudes were consistent with the modern values, with a standard deviation of 2 degrees. The longitudes, on the other hand, were systematically shifted, consistent with the choice of the Fortunate Isles (Canary Islands) as the Prime Meridian. The average value of this offset is 23 degrees west, with an uncertainty in the offset of 1.3 degrees. The standard deviation for the longitude difference is 7 degrees.
Since measurements of latitude are typically done by celestial techniques, it’s no surprise that the values are better than longitude. We cannot exclude that some of the measurements of latitude were done via dead reckoning relative to some nearby city. Longitude is not as precise, since one assumes that most of these are derived from dead reckoning.
The scatter plot of longitude versus latitude differences and my thinking on each of the entries appears below in the text.
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