I'm having trouble calculating distances on hex-mapped worlds. The math, even at the regional scale, is difficult.
But I'm also interested in distances at the world-scale. I'm targeting icosahedral maps of planets / worlds in particular. I'm looking for distance calculations "as the crow flies" regardless of obstacles, as opposed to the length of the most direct valid path.
How do such programs as "Traveller Heaven & Earth" calculate the various distances between hexes, particularly at the planet-scale (with those odd pentagons getting into the path)? Perhaps there is some material on this topic in classical tabletop/boardgame stuff, but I never played such games and thus have no access to such material yet.
Any hints on this?