/*::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
/*::                                                                         :*/
/*::  This routine calculates the distance between two points (given the     :*/
/*::  latitude/longitude of those points). It is being used to calculate     :*/
/*::  the distance between two locations using GeoDataSource (TM) prodducts  :*/
/*::                                                                         :*/
/*::  Definitions:                                                           :*/
/*::    South latitudes are negative, east longitudes are positive           :*/
/*::                                                                         :*/
/*::  Passed to function:                                                    :*/
/*::    lat1, lon1 = Latitude and Longitude of point 1 (in decimal degrees)  :*/
/*::    lat2, lon2 = Latitude and Longitude of point 2 (in decimal degrees)  :*/
/*::    unit = the unit you desire for results                               :*/
/*::           where: 'M' is statute miles (default)                         :*/
/*::                  'K' is kilometers                                      :*/
/*::                  'N' is nautical miles                                  :*/
/*::  Worldwide cities and other features databases with latitude longitude  :*/
/*::  are available at http://www.geodatasource.com                          :*/
/*::                                                                         :*/
/*::  For enquiries, please contact sales@geodatasource.com                  :*/
/*::                                                                         :*/
/*::  Official Web site: http://www.geodatasource.com                        :*/
/*::                                                                         :*/
/*::           GeoDataSource.com (C) All Rights Reserved 2015                :*/
/*::                                                                         :*/
/*::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/

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);
}

/*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
/*::  This function converts decimal degrees to radians             :*/
/*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
private double deg2rad(double deg) {
  return (deg * Math.PI / 180.0);
}

/*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
/*::  This function converts radians to decimal degrees             :*/
/*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
private double rad2deg(double rad) {
  return (rad * 180 / Math.PI);
}

system.println(distance(32.9697, -96.80322, 29.46786, -98.53506, "M") + " Miles\n");
system.println(distance(32.9697, -96.80322, 29.46786, -98.53506, "K") + " Kilometers\n");
system.println(distance(32.9697, -96.80322, 29.46786, -98.53506, "N") + " Nautical Miles\n");