code: function distance(lat1, lon1, lat2, lon2) {
    let R = 6371; // Radius of the earth in km
    let dLat = _deg2rad(lat2-lat1);  // deg2rad below
    let dLon = _deg2rad(lon2-lon1);
    let a =
      Math.sin(dLat/2) * Math.sin(dLat/2) +
      Math.cos(_deg2rad(lat1)) * Math.cos(_deg2rad(lat2)) *
      Math.sin(dLon/2) * Math.sin(dLon/2)
    ;
    let c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    let d = R * c; // Distance in km
    return d * 0.621371; // Return distance in miles
  }
docs: Right Track calculation helper functions
  @module utils/calc
   
  Calculate the (Great-Circle) Distance between two points
  @param {number} lat1 Latitude of Point 1
  @param {number} lon1 Longitude of Point 1
  @param {number} lat2 Latitude of Point 2
  @param {number} lon2 Longitude of Point 2
  @returns {number} distance between points in miles