var getDistance = function(p1, p2) {
  var R = 6378137; // Earth’s mean radius in meter
  var dLat = rad(p2.lat() - p1.lat());
  var dLong = rad(p2.lng() - p1.lng());
  var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
    Math.cos(rad(p1.lat())) * Math.cos(rad(p2.lat())) *
    Math.sin(dLong / 2) * Math.sin(dLong / 2);
  var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  var d = R * c;
  return d; // returns the distance in meter
};

$formula = $radius." * (2 * ATAN2(SQRT(POW(SIN(RADIANS(`coor_x` - ".$main_lat.")), 2) +
					COS(RADIANS(".$main_lat.")) * COS(RADIANS(`coor_x`)) * POW(SIN(RADIANS(`coor_y` - ".$main_lgn.") / 2), 2),
                    SQRT(1 - POW(SIN(RADIANS(`coor_x` - ".$main_lat.")), 2)) + 
					COS(RADIANS(".$main_lat.")) * COS(RADIANS(`coor_x`)) * POW(SIN(RADIANS(`coor_y` - ".$main_lgn.") / 2), 2))))";

$sth = $dbh->prepare("SELECT `point_id`, `point_name`, `coor_x`, `coor_y` FROM `points_table`   WHERE (".$formula.") < 1000");