參考: https://stackoverflow.com/questions/6671183/calculate-the-center-point-of-multiple-latitude-longitude-coordinate-pairs
Python Java C# JavaScript Objective-C PHP 版本均有

function GetCenterFromDegrees($data){
    
    if (!is_array($data)) return FALSE;

    $num_coords = count($data);

    $X
 
 = 0.0;
    $Y = 0.0;
    $Z = 0.0;

    foreach ($data as $coord){
        
        $lat = deg2rad((float)$coord[0]);
        $lon = deg2rad((float)$coord[1]);

        $a = cos($lat) * cos($lon);
        $b = cos($lat) * sin($lon);
        $c = sin($lat);

        $X += $a;
        $Y += $b;
        $Z +
 
= $c;
    }

    $X /= $num_coords;
    $Y /= $num_coords;
    $Z /= $num_coords;

    $lon = atan2($Y, $X);
    $hyp = sqrt($X * $X + $Y * $Y);
    $lat = atan2($Z, $hyp);

    return array(rad2deg($lat), rad2deg($lon));
}

// 測試資料
$data = array(
    array(45.849382, 76.322333),
    array(45.843543, 75.324143
 
),
    array(45.765744, 76.543223),
    array(45.784234, 74.542335)
);

print_r(GetCenterFromDegrees($data));
// Array ( [0] => 45.813538469271 [1] => 75.682996448603 )