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)
}
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
return the Ersatz ( squared ) distance between two stops in undefined units