code: public static double haversineFormulaDeg(double lat1, double lon1, double lat2, double lon2) {
      return haversineFormulaRad(deg2rad(lat1), deg2rad(lon1), deg2rad(lat2), deg2rad(lon2));
    }
docs: Compute the approximate great-circle distance of two points using the
  Haversine formula
  <p>
  Complexity: 5 trigonometric functions, 1 sqrt.
  <p>
  Reference:
  <p>
  R. W. Sinnott,<br>
  Virtues of the Haversine<br>
  Sky and Telescope 68(2)
  
  @param lat1 Latitude of first point in degree
  @param lon1 Longitude of first point in degree
  @param lat2 Latitude of second point in degree
  @param lon2 Longitude of second point in degree
  @return Distance on unit sphere