Calculate the straight-line (great-circle) distance between two GPS coordinates using the Haversine formula. Returns meters, km, miles, and compass bearing. No external API.
POST /maps/distance computes the Haversine (great-circle) distance between two coordinate pairs. All computation is done server-side with no external API calls. Also returns compass bearing (N, NE, E, SE, S, SW, W, NW) and bearing in degrees.