public function set_values_from_point(lat_lng $point)
{
$this->OS6 = geometry::lat_long_to_os($point, 6);
$this->OS8 = geometry::lat_long_to_os($point, 8);
$this->WGS84_lat = $point->lat();
$this->WGS84_lng = $point->lng();
$osgb36 = gps_datums::convert($point, 'WGS84', 'OSGB36');
$this->OSGB36_lat = $osgb36->lat();
$this->OSGB36_lng = $osgb36->lng();
}
/**
* @param string $gridRef
* @return lat_lng
*/
static function os_to_lat_long($gridRef)
{
$gr = self::gridref_letter_to_number($gridRef);
$E = $gr[0];
$N = $gr[1];
$a = 6377563.396;
$b = 6356256.91;
// Airy 1830 major & minor semi-axes
$F0 = 0.9996012717;
// NatGrid scale factor on central meridian
$lat0 = 49 * M_PI / 180;
$lon0 = -2 * M_PI / 180;
// NatGrid true origin
$N0 = -100000;
$E0 = 400000;
// northing & easting of true origin; metres
$e2 = 1 - $b * $b / ($a * $a);
// eccentricity squared
$n = ($a - $b) / ($a + $b);
$n2 = $n * $n;
$n3 = $n * $n * $n;
$lat = $lat0;
$M = 0;
do {
$lat = ($N - $N0 - $M) / ($a * $F0) + $lat;
$Ma = (1 + $n + 5 / 4 * $n2 + 5 / 4 * $n3) * ($lat - $lat0);
$Mb = (3 * $n + 3 * $n * $n + 21 / 8 * $n3) * sin($lat - $lat0) * cos($lat + $lat0);
$Mc = (15 / 8 * $n2 + 15 / 8 * $n3) * sin(2 * ($lat - $lat0)) * cos(2 * ($lat + $lat0));
$Md = 35 / 24 * $n3 * sin(3 * ($lat - $lat0)) * cos(3 * ($lat + $lat0));
$M = $b * $F0 * ($Ma - $Mb + $Mc - $Md);
// meridional arc
} while ($N - $N0 - $M >= 1.0E-5);
// ie until < 0.01mm
$cosLat = cos($lat);
$sinLat = sin($lat);
$nu = $a * $F0 / sqrt(1 - $e2 * $sinLat * $sinLat);
// transverse radius of curvature
$rho = $a * $F0 * (1 - $e2) / pow(1 - $e2 * $sinLat * $sinLat, 1.5);
// meridional radius of curvature
$eta2 = $nu / $rho - 1;
$tanLat = tan($lat);
$tan2lat = $tanLat * $tanLat;
$tan4lat = $tan2lat * $tan2lat;
$tan6lat = $tan4lat * $tan2lat;
$secLat = 1 / $cosLat;
$nu3 = $nu * $nu * $nu;
$nu5 = $nu3 * $nu * $nu;
$nu7 = $nu5 * $nu * $nu;
$VII = $tanLat / (2 * $rho * $nu);
$VIII = $tanLat / (24 * $rho * $nu3) * (5 + 3 * $tan2lat + $eta2 - 9 * $tan2lat * $eta2);
$IX = $tanLat / (720 * $rho * $nu5) * (61 + 90 * $tan2lat + 45 * $tan4lat);
$X = $secLat / $nu;
$XI = $secLat / (6 * $nu3) * ($nu / $rho + 2 * $tan2lat);
$XII = $secLat / (120 * $nu5) * (5 + 28 * $tan2lat + 24 * $tan4lat);
$XIIA = $secLat / (5040 * $nu7) * (61 + 662 * $tan2lat + 1320 * $tan4lat + 720 * $tan6lat);
$dE = $E - $E0;
$dE2 = $dE * $dE;
$dE3 = $dE2 * $dE;
$dE4 = $dE2 * $dE2;
$dE5 = $dE3 * $dE2;
$dE6 = $dE4 * $dE2;
$dE7 = $dE5 * $dE2;
$lat = $lat - $VII * $dE2 + $VIII * $dE4 - $IX * $dE6;
$lon = $lon0 + $X * $dE - $XI * $dE3 + $XII * $dE5 - $XIIA * $dE7;
return gps_datums::convert(new lat_lng(rad2deg($lat), rad2deg($lon)), 'OSGB36', 'WGS84');
}