Come ottenere 2 o 3 punti centrali della posizione radiale (Latitudine, Longitudine)

Ho controllato questo esempio:http://geomidpoint.com/example.html

E ho scritto una funzione in PHP, spero che sia utile ...

[modifica] ho dimenticato di convertire in radianti per i calcoli, quindi ha dato un output diverso, quindi ora dovrebbe funzionare bene ...

   <?php

function middlepoint($lat1,$lon1,$lat2,$lon2,$lat3,$lon3){
    $w1=1095.75;$w2=730.5;$w3=365.25;$tw=$w1+$w2+$w3;   //weighting factors

    $x1=cos(floatval(deg2rad($lat1)))*cos(floatval(deg2rad($lon1)));$y1=cos(floatval(deg2rad($lat1)))*sin(floatval(deg2rad($lon1)));$z1=sin(floatval(deg2rad($lat1)));$x2=cos(floatval(deg2rad($lat2)))*cos(floatval(deg2rad($lon2)));$y2=cos(floatval(deg2rad($lat2)))*sin(floatval(deg2rad($lon2)));$z2=sin(floatval(deg2rad($lat2)));$x3=cos(floatval(deg2rad($lat3)))*cos(floatval(deg2rad($lon3)));$y3=cos(floatval(deg2rad($lat3)))*sin(floatval(deg2rad($lon3)));$z3=sin(floatval(deg2rad($lat3)));  //convert lat/long to cartesian (x,y,z) coordinates

    $x = ($x1*$w1+$x2*$w2+$x3*$w3)/$tw;$y=($y1*$w1+$y2*$w2+$y3*$w3)/$tw;$z=($z1*$w1+$z2*$w2+$z3*$w3)/$tw;   //Compute combined weighted cartesian coordinates

    $lon=atan2($y,$x);$hyp=sqrt(pow($x,2)+pow($y,2));$lat=atan2($z,$hyp);   //Convert cartesian coordinate to latitude and longitude for the midpoint

    $midpoint[0] = $lon * (180/pi());$midpoint[1] = $lat * (180/pi());  //Convert from radians to degrees

    return $midpoint;   //return an array(lat,lon);

}

$test = middlepoint(41.040035,28.984026,41.040868,28.985807,41.039136,28.984981);
print_r($test);

?>