calc distances

distanceTo.ts

  public distanceTo = function(endLat, endLon, startLat, startLon){

    endLat = Number(endLat);
    endLon = Number(endLon);
    startLat = Number(startLat);
    startLon = Number(startLon);

    var R = 6371e3; // metres
    var φ1 = startLat * Math.PI / 180;
    var φ2 = endLat * Math.PI / 180;
    var Δφ = (endLat-startLat) * Math.PI / 180;
    var Δλ = (endLon-startLon) * Math.PI / 180;
    var a = Math.sin(Δφ/2) * Math.sin(Δφ/2) +
      Math.cos(φ1) * Math.cos(φ2) *
      Math.sin(Δλ/2) * Math.sin(Δλ/2);
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    var d = R * c;

    d = d * 0.000621371192; //convert to miles

    return d;
  };