[TorpX]

I just read your post don. I don't understand it at all.

I know a great circle route will not be a straight line on a mercator chart, and that this is vital in real world navigation. But I don't see how any of this applies to SH3/SH4. When I checked distances in SH4, I saw clearly that the meridians do not converge anywhere on the map. One degree of lat. or lon. is the same distance everywhere. For all practical purposes, the SH4 world is flat.
Perhaps I should say it's cylendrical, as you can go around the world east to west, but as I said above, every grid square is the same size as every other in the game.

Have you tried to verify your gnomonic idea?

Unless I am very much mistaken, your marked route from San Francisco to Yokohama, will add many extra miles to your cruise in SH4.