Paleocartography? Longitued BCE?

[waldronate]

Welcome to the guild!

I can't even think how one might go about determining paleolongitude (differences and applying differences to an absolute reference point is hugely fraught with errors). Paleolatitude is bad enough and also full of with errors. Latitude is a nice physical quantity that has measurable characteristics, but Longitude is an arbitrary convention with 0 being at some culturally-defined location.

Having said that, this is a good location to discuss such things. There's always interest and some of the folks hereabouts are pretty sharp on those kinds of subjects.

[Mathus]

I'm not sure that I can really see the problem here.

Are you talking about "Defining longitude using the reference system of ancient civilisations"?
If so then this is just a maths problem. Involved to be sure but straight forward, just read a book on trigonometry and pick your chosen points of origin.

If you are talking about "Where did this piece of continental crust come from?" then that is a different kettle of fish entirely and is more about working backwards form the current physical density maps of today's tectonic plates, figuring out the current stresses and strains, running those as reverse accelerations and accounting for the fact that those stresses and strains will result in density changes to the plates which themselves will results in new forces. To ensure accuracy the historical densities of rock can be used, "How long ago was it since the density of this piece of crust changed, as determined by the current magnetic resonance and chemical composition."
This is sort of like weather modelling but in reverse. If your data are inaccurate by any amount then you will obtain very different results. However unlike modelling future weather you can 'calibrate' the model by looking at known historical data. Again though, if the historical data are inaccurate so will your model be.
Be aware that people spend millions trying to predict the weather and are generally only usefully accurate to 1-5 days. Rock moves slower but like any fluidic system it is chaotic so don't expect useful results beyond 30-50 'movement iterations'.
As far as I know a movement iteration for weather (air) is an hour. For plate tectonics (rock) it may be 100-300 years, depends on how fine grained your model is. Again though if your model is not detailed enough it will be too inaccurate to be of use.