lib/get-transitive-data.js
function stopDistance (s1: Stop, s2: Stop): number {
  const cosLat = Math.cos(s1.stop_lat * Math.PI / 180)
  return Math.pow(s1.stop_lat - s2.stop_lat, 2) + Math.pow(s1.stop_lon * cosLat - s2.stop_lon * cosLat, 2)
}
function stopDistance (s1: Stop, s2: Stop): number {
  const cosLat = Math.cos(s1.stop_lat * Math.PI / 180)
  return Math.pow(s1.stop_lat - s2.stop_lat, 2) + Math.pow(s1.stop_lon * cosLat - s2.stop_lon * cosLat, 2)
}
return the Ersatz (squared) distance between two stops, in undefined units