Where Would Surviving Roman Empire Place its Prime Meridian?

Assume a unified Roman Empire, encompassing, at minimum, its ‘usual borders,’ and surviving to the present. Where would this Empire likely pick its Prime Meridian to run through?

To me, this would likely be determined by either politics or convenience - the latter more about where the corresponding international date line would end up. The only difficult points I can imagine would be Constantinople or Jerusalem. As it is, running it through Rome results in Alaska being in the Eastern Hemisphere, but the IDL can be squiggly.

On thay note, I could also see Roman cartographers picking an arbitrary point, such as the westernmost point in Mainland Europe or Africa, simply to keep the whole continent(s) in the same hemisphere. That would result in some corresponding squiggliness with Kamchatka being in the Western Hemisphere.
 
Probably the Ferro Meridian, which in Antiquity was cited by Ptolemy as the westernmost part of the known world. Notably, France and Germany used variants of the Ferro meridian, and since Rome is about 12'30 E and Ferro is about 18'09 W, Rome might use a variant of it which makes the Meridian perhaps at 18'30 W, like how at one point "Germanic" Europe calculated it at 17'40 W.

The other potentials are Rome itself, or maybe Jerusalem assuming a Christian Rome. A very "scientific" Roman Empire, the sort which would demand and enforce metrification, would likely mount expeditions along the equator to find the highest point along there to use as the meridian, and thus sooner or later choose the southern slopes of the Ecuadorian mountain Cayambe at about 78 W as the Prime Meridian. This would be later in history, but there was no solid prime meridian until the late 19th century OTL, so maybe Rome might compromise with the usual great powers in a "Rome survives" setting (China, Inca, etc.) and go for a more scientific rather than arbitrary definition, even though OTL less official prime meridians were common throughout history before the official one was set.
 
Probably the Ferro Meridian, which in Antiquity was cited by Ptolemy as the westernmost part of the known world. Notably, France and Germany used variants of the Ferro meridian, and since Rome is about 12'30 E and Ferro is about 18'09 W, Rome might use a variant of it which makes the Meridian perhaps at 18'30 W, like how at one point "Germanic" Europe calculated it at 17'40 W.

The other potentials are Rome itself, or maybe Jerusalem assuming a Christian Rome. A very "scientific" Roman Empire, the sort which would demand and enforce metrification, would likely mount expeditions along the equator to find the highest point along there to use as the meridian, and thus sooner or later choose the southern slopes of the Ecuadorian mountain Cayambe at about 78 W as the Prime Meridian. This would be later in history, but there was no solid prime meridian until the late 19th century OTL, so maybe Rome might compromise with the usual great powers in a "Rome survives" setting (China, Inca, etc.) and go for a more scientific rather than arbitrary definition, even though OTL less official prime meridians were common throughout history before the official one was set.

That almost perfectly lines up with the weaternmost point in Africa, too. Very handy.
 
Top