get_distance_meters function : get distance in MySQL

get_distance_meters

DELIMITER //

/*
Exemple :
You have table city with latitude and longitude column.
get_distance_meters(my_latitude, my_longitude, city.latitude, city.longitude)
return the distance in km
*/        
CREATE  FUNCTION  get_distance_meters ( lat1 FLOAT, lon1 FLOAT, lat2 FLOAT, lon2 FLOAT ) RETURNS  DOUBLE PRECISION
BEGIN
  DECLARE pi, q1, q2, q3  DOUBLE PRECISION;
  DECLARE rads  DOUBLE PRECISION DEFAULT 0;
  SET pi = PI();
  SET lat1 = lat1 * pi / 180;
  SET lon1 = lon1 * pi / 180;
  SET lat2 = lat2 * pi / 180;
  SET lon2 = lon2 * pi / 180;
  SET q1 = COS(lon1-lon2);
  SET q2 = COS(lat1-lat2);
  SET q3 = COS(lat1+lat2);
  SET rads = ACOS( 0.5*((1.0+q1)*q2 - (1.0-q1)*q3) );
  RETURN 6378.388 * rads;
END//