You get to keep your bottle of port.

Hapgood's book was full of crap in a number of respects and, as I recall, it had the scientific rigour typical of the 'spacegods' genre, which is to say little to none, but those maps were very thought-provoking and stood alone.

I have to reiterate that my investigations took place more years ago than I care to remember and the intervening decades have dulled my memory of, and enthusiasm for, the topic. It is by no means a current interest for me, so I may not be the muse you are looking for. I have no idea at this stage whether I ever read the books you mention. Perhaps I'll put them on the list to check out when I retire.

I don't recall reading about the exact method you suggest, but that's not to say it's new, and I have vague recollections that other methods may have used solar midnight as a marker.

A brief consideration of your method leads me to conclude that it seems to be scientifically valid, though I probably haven't absorbed the finer nuances of your ideas and at present my interest is not rekindled sufficiently to check your figures regarding accuracy and error margins. Error analysis is a PITA even for a current project.

Of course, whilst this method (and others) would make for more accurate cartography, it doesn't address the problem of determining longitude at sea, which was always the real 'holy grail'.

I'm happy to discuss the topic, it makes for interesting conversation, but I'm probably not going to spend time doing calculations on it. As I said upthread, I concluded long ago that land-based, and to an extent, sea-based longitude determination was possible before the current era, that others had reached similar conclusions, and that there was little point in re-inventing the wheel. But my goal, even back then, was only to satisfy myself that it was possible, not to achieve 'fame and fortune' by writing a rigorous scientific paper on the subject.
For me, it's just another windmill carved on my lance.

What drives your interest in this material? How do you define 'making your mark in paleocartography'?

If you want to set out any calculations I might be tempted to confirm them, if that's helpful to you, provided I don't have to go digging out any books and we don't stray into spherical geometry. That stuff used to hurt my head even when it was young and pliable.

BTW, if you run out of bytes, there's nothing to prevent you from spilling over into a second, or third post, we don't have thought police here.