/**
* Convert this grid reference into a latitude and longitude
*
* @return
*/
function toLatLng()
{
$airy1830 = new RefEll(6377563.396, 6356256.909);
$OSGB_F0 = 0.9996012717;
$N0 = -100000.0;
$E0 = 400000.0;
$phi0 = deg2rad(49.0);
$lambda0 = deg2rad(-2.0);
$a = $airy1830->maj;
$b = $airy1830->min;
$eSquared = $airy1830->ecc;
$phi = 0.0;
$lambda = 0.0;
$E = $this->easting;
$N = $this->northing;
$n = ($a - $b) / ($a + $b);
$M = 0.0;
$phiPrime = ($N - $N0) / ($a * $OSGB_F0) + $phi0;
do {
$M = $b * $OSGB_F0 * ((1 + $n + 5.0 / 4.0 * $n * $n + 5.0 / 4.0 * $n * $n * $n) * ($phiPrime - $phi0) - (3 * $n + 3 * $n * $n + 21.0 / 8.0 * $n * $n * $n) * sin($phiPrime - $phi0) * cos($phiPrime + $phi0) + (15.0 / 8.0 * $n * $n + 15.0 / 8.0 * $n * $n * $n) * sin(2.0 * ($phiPrime - $phi0)) * cos(2.0 * ($phiPrime + $phi0)) - 35.0 / 24.0 * $n * $n * $n * sin(3.0 * ($phiPrime - $phi0)) * cos(3.0 * ($phiPrime + $phi0)));
$phiPrime += ($N - $N0 - $M) / ($a * $OSGB_F0);
} while ($N - $N0 - $M >= 0.001);
$v = $a * $OSGB_F0 * pow(1.0 - $eSquared * coordHelpers::sinSquared($phiPrime), -0.5);
$rho = $a * $OSGB_F0 * (1.0 - $eSquared) * pow(1.0 - $eSquared * coordHelpers::sinSquared($phiPrime), -1.5);
$etaSquared = $v / $rho - 1.0;
$VII = tan($phiPrime) / (2 * $rho * $v);
$VIII = tan($phiPrime) / (24.0 * $rho * pow($v, 3.0)) * (5.0 + 3.0 * coordHelpers::tanSquared($phiPrime) + $etaSquared - 9.0 * coordHelpers::tanSquared($phiPrime) * $etaSquared);
$IX = tan($phiPrime) / (720.0 * $rho * pow($v, 5.0)) * (61.0 + 90.0 * coordHelpers::tanSquared($phiPrime) + 45.0 * coordHelpers::tanSquared($phiPrime) * coordHelpers::tanSquared($phiPrime));
$X = coordHelpers::sec($phiPrime) / $v;
$XI = coordHelpers::sec($phiPrime) / (6.0 * $v * $v * $v) * ($v / $rho + 2 * coordHelpers::tanSquared($phiPrime));
$XII = coordHelpers::sec($phiPrime) / (120.0 * pow($v, 5.0)) * (5.0 + 28.0 * coordHelpers::tanSquared($phiPrime) + 24.0 * coordHelpers::tanSquared($phiPrime) * coordHelpers::tanSquared($phiPrime));
$XIIA = coordHelpers::sec($phiPrime) / (5040.0 * pow($v, 7.0)) * (61.0 + 662.0 * coordHelpers::tanSquared($phiPrime) + 1320.0 * coordHelpers::tanSquared($phiPrime) * coordHelpers::tanSquared($phiPrime) + 720.0 * coordHelpers::tanSquared($phiPrime) * coordHelpers::tanSquared($phiPrime) * coordHelpers::tanSquared($phiPrime));
$phi = $phiPrime - $VII * pow($E - $E0, 2.0) + $VIII * pow($E - $E0, 4.0) - $IX * pow($E - $E0, 6.0);
$lambda = $lambda0 + $X * ($E - $E0) - $XI * pow($E - $E0, 3.0) + $XII * pow($E - $E0, 5.0) - $XIIA * pow($E - $E0, 7.0);
return new LatLng(rad2deg($phi), rad2deg($lambda));
}
/**
* Convert a latitude and longitude to an UTM reference
*
* @return the converted UTM reference
*/
function toUTMRef()
{
$wgs84 = new RefEll(6378137, 6356752.314);
$UTM_F0 = 0.9996;
$a = $wgs84->maj;
$eSquared = $wgs84->ecc;
$longitude = $this->lng;
$latitude = $this->lat;
$latitudeRad = $latitude * (pi() / 180.0);
$longitudeRad = $longitude * (pi() / 180.0);
$longitudeZone = (int) (($longitude + 180.0) / 6.0) + 1;
// Special zone for Norway
if ($latitude >= 56.0 && $latitude < 64.0 && $longitude >= 3.0 && $longitude < 12.0) {
$longitudeZone = 32;
}
// Special zones for Svalbard
if ($latitude >= 72.0 && $latitude < 84.0) {
if ($longitude >= 0.0 && $longitude < 9.0) {
$longitudeZone = 31;
} else {
if ($longitude >= 9.0 && $longitude < 21.0) {
$longitudeZone = 33;
} else {
if ($longitude >= 21.0 && $longitude < 33.0) {
$longitudeZone = 35;
} else {
if ($longitude >= 33.0 && $longitude < 42.0) {
$longitudeZone = 37;
}
}
}
}
}
$longitudeOrigin = ($longitudeZone - 1) * 6 - 180 + 3;
$longitudeOriginRad = $longitudeOrigin * (pi() / 180.0);
$UTMZone = coordHelpers::getUTMLatitudeZoneLetter($latitude);
$ePrimeSquared = $eSquared / (1 - $eSquared);
$n = $a / sqrt(1 - $eSquared * sin($latitudeRad) * sin($latitudeRad));
$t = tan($latitudeRad) * tan($latitudeRad);
$c = $ePrimeSquared * cos($latitudeRad) * cos($latitudeRad);
$A = cos($latitudeRad) * ($longitudeRad - $longitudeOriginRad);
$M = $a * ((1 - $eSquared / 4 - 3 * $eSquared * $eSquared / 64 - 5 * $eSquared * $eSquared * $eSquared / 256) * $latitudeRad - (3 * $eSquared / 8 + 3 * $eSquared * $eSquared / 32 + 45 * $eSquared * $eSquared * $eSquared / 1024) * sin(2 * $latitudeRad) + (15 * $eSquared * $eSquared / 256 + 45 * $eSquared * $eSquared * $eSquared / 1024) * sin(4 * $latitudeRad) - 35 * $eSquared * $eSquared * $eSquared / 3072 * sin(6 * $latitudeRad));
$UTMEasting = (double) ($UTM_F0 * $n * ($A + (1 - $t + $c) * pow($A, 3.0) / 6 + (5 - 18 * $t + $t * $t + 72 * $c - 58 * $ePrimeSquared) * pow($A, 5.0) / 120) + 500000.0);
$UTMNorthing = (double) ($UTM_F0 * ($M + $n * tan($latitudeRad) * ($A * $A / 2 + (5 - $t + 9 * $c + 4 * $c * $c) * pow($A, 4.0) / 24 + (61 - 58 * $t + $t * $t + 600 * $c - 330 * $ePrimeSquared) * pow($A, 6.0) / 720)));
// Adjust for the southern hemisphere
if ($latitude < 0) {
$UTMNorthing += 10000000.0;
}
return new UTMRef($UTMEasting, $UTMNorthing, $UTMZone, $longitudeZone);
}
