Inspired by a comment by hupakee@lemmy.world under SurrealPartisan’s recent post in this community
The longest straight line over land is this great circle (see NeatNit’s comment here if the link isn’t working for you, sorry about that). But, of course, most great circles don’t look very straight on most maps. To correct for this, I (very roughly) got the northernmost point of the great circle and put that value into G.Projector to get an oblique equirectangular projection that treats the great circle as if it were the equator on a regular map
The base map is Wikimedia Commons’ equirectangular projection map


Managed to work it out, here’s the fixed link:
www.gcmap.com/mapui?P=5%B02%2751.59%22N+9%B07%2723.26%22W-28%B017%277.68%22N+121%B038%2717.31%22E&MS=wls&DU=miApparently Lemmy is screwing something up with the link. If you paste it into a comment, it gets modified.
Edit: okay, what the hell.
The query string starts with:
P=5%B02%27But this gets converted to:
http://example.com/?P=5%EF%BF%BD2%27Ahh, if it’s an issue with lemmy then that would explain why it’s working for me. I’ll add that as an alternative link in the post body
yeah I’m still playing with it, seems like a really serious lemmy bug. I’ll report it.