public function computeMissing()
    {
        $Missing = [];
        for ($X = 0; $X <= $this->GridSizeX; $X++) {
            for ($Y = 0; $Y <= $this->GridSizeY; $Y++) {
                if ($this->Points[$X][$Y] == UNKNOWN) {
                    $Missing[] = $X . "," . $Y;
                }
            }
        }
        shuffle($Missing);

        foreach ($Missing as $Pos) {
            $Pos = preg_split("/,/", $Pos);
            $X = $Pos[0];
            $Y = $Pos[1];

            if ($this->Points[$X][$Y] == UNKNOWN) {
                $NearestNeighbor = $this->getNearestNeighbor($X, $Y);

                $Value = 0;
                $Points = 0;
                for ($Xi = $X - $NearestNeighbor; $Xi <= $X + $NearestNeighbor; $Xi++) {
                    for ($Yi = $Y - $NearestNeighbor; $Yi <= $Y + $NearestNeighbor; $Yi++) {
                        if ($Xi >= 0
                            && $Yi >= 0
                            && $Xi <= $this->GridSizeX
                            && $Yi <= $this->GridSizeY
                            && $this->Points[$Xi][$Yi] != UNKNOWN
                            && $this->Points[$Xi][$Yi] != IGNORED
                        ) {
                            $Value = $Value + $this->Points[$Xi][$Yi];
                            $Points++;
                        }
                    }
                }

                if ($Points != 0) {
                    $this->Points[$X][$Y] = $Value / $Points;
                }
            }
        }
    }