function getDistance(c1, c2, radius) {
  radius = radius || DEFAULT_RADIUS;
  const lat1 = toRadians(c1[1]);
  const lat2 = toRadians(c2[1]);
  const deltaLatBy2 = (lat2 - lat1) / 2;
  const deltaLonBy2 = toRadians(c2[0] - c1[0]) / 2;
  const a =
    Math.sin(deltaLatBy2) * Math.sin(deltaLatBy2) +
    Math.sin(deltaLonBy2) *
      Math.sin(deltaLonBy2) *
      Math.cos(lat1) *
      Math.cos(lat2);
  return 2 * radius * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
}
Get the great circle distance (in meters) between two geographic coordinates.
@param {Array} c1 Starting coordinate.
@param {Array} c2 Ending coordinate.
@param {number} [radius] The sphere radius to use.  Defaults to the Earth's
    mean radius using the WGS84 ellipsoid.
@return {number} The great circle distance between the points (in meters).
@api