private double distance(double lat1, double lon1, double lat2, double lon2, char unit) {
		  double theta = lon1 - lon2;
		  double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2)) + Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * Math.cos(deg2rad(theta));
		  dist = Math.acos(dist);
		  dist = rad2deg(dist);
		  dist = dist * 60 * 1.1515;
		  if (unit == 'K') {
		    dist = dist * 1.609344;
		  } else if (unit == 'N') {
		  	dist = dist * 0.8684;
		    }
		  return (dist);
	}