function E_N_to_Long($East, $North, $a, $b, $e0, $n0, $f0, $PHI0, $LAM0)
{
#Un-project Transverse Mercator eastings and northings back to longitude.
#Input: - _
#eastings (East) and northings (North) in meters; _
#ellipsoid axis dimensions (a & b) in meters; _
#eastings (e0) and northings (n0) of false origin in meters; _
#central meridian scale factor (f0) and _
#latitude (PHI0) and longitude (LAM0) of false origin in decimal degrees.
#REQUIRES THE "Marc" AND "InitialLat" FUNCTIONS
#Convert angle measures to radians
$Pi = 3.14159265358979;
$RadPHI0 = $PHI0 * ($Pi / 180);
$RadLAM0 = $LAM0 * ($Pi / 180);
#Compute af0, bf0, e squared (e2), n and Et
$af0 = $a * $f0;
$bf0 = $b * $f0;
$e2 = (pow($af0, 2) - pow($bf0, 2)) / pow($af0, 2);
$n = ($af0 - $bf0) / ($af0 + $bf0);
$Et = $East - $e0;
#Compute initial value for latitude (PHI) in radians
$PHId = $this->InitialLat($North, $n0, $af0, $RadPHI0, $n, $bf0);
#Compute nu, rho and eta2 using value for PHId
$nu = $af0 / sqrt(1 - $e2 * pow(sin($PHId), 2));
$rho = $nu * (1 - $e2) / (1 - $e2 * pow(Sin($PHId), 2));
$eta2 = $nu / $rho - 1;
#Compute Longitude
$X = pow(cos($PHId), -1) / $nu;
$XI = pow(cos($PHId), -1) / (6 * pow($nu, 3)) * ($nu / $rho + 2 * pow(tan($PHId), 2));
$XII = pow(cos($PHId), -1) / (120 * pow($nu, 5)) * (5 + 28 * pow(tan($PHId), 2) + 24 * pow(tan($PHId), 4));
$XIIA = pow(Cos($PHId), -1) / (5040 * pow($nu, 7)) * (61 + 662 * pow(tan($PHId), 2) + 1320 * pow(Tan($PHId), 4) + 720 * pow(tan($PHId), 6));
$E_N_to_Long = 180 / $Pi * ($RadLAM0 + $Et * $X - pow($Et, 3) * $XI + pow($Et, 5) * $XII - pow($Et, 7) * $XIIA);
return $E_N_to_Long;
}
/** Un-project Transverse Mercator eastings and northings back to longitude.
* @uses marc
* @uses InitialLat
* @param string $East easting in metres
* @param string $North northing in metres
* @param string $a ellipsoid axis in metres
* @param string $b ellipsoid axis in metres
* @param string $e0 eastings false origin
* @param string $n0 northings false origin
* @param integer $f0 central meridian scale factor
* @param double $PHI0 latitude of false origin in dec degrees
* @param double $LAM0 longitude of false origin in dec degrees
*/
private function _eNtoLong($East, $North, $a, $b, $e0, $n0, $f0, $PHI0, $LAM0)
{
//Convert angle measures to radians
$RadPHI0 = $PHI0 * (self::PI / 180);
$RadLAM0 = $LAM0 * (self::PI / 180);
//Compute af0, bf0, e squared (e2), n and Et
$af0 = $a * $f0;
$bf0 = $b * $f0;
$e2 = (pow($af0, 2) - pow($bf0, 2)) / pow($af0, 2);
$n = ($af0 - $bf0) / ($af0 + $bf0);
$Et = $East - $e0;
//Compute initial value for latitude (PHI) in radians
$PHId = $this->_initialLat($North, $n0, $af0, $RadPHI0, $n, $bf0);
//Compute nu, rho and eta2 using value for PHId
$nu = $af0 / sqrt(1 - $e2 * pow(sin($PHId), 2));
$rho = $nu * (1 - $e2) / (1 - $e2 * pow(Sin($PHId), 2));
$eta2 = $nu / $rho - 1;
//Compute Longitude
$X = pow(cos($PHId), -1) / $nu;
$XI = pow(cos($PHId), -1) / (6 * pow($nu, 3)) * ($nu / $rho + 2 * pow(tan($PHId), 2));
$XII = pow(cos($PHId), -1) / (120 * pow($nu, 5)) * (5 + 28 * pow(tan($PHId), 2) + 24 * pow(tan($PHId), 4));
$XIIA = pow(Cos($PHId), -1) / (5040 * pow($nu, 7)) * (61 + 662 * pow(tan($PHId), 2) + 1320 * pow(Tan($PHId), 4) + 720 * pow(tan($PHId), 6));
$E_N_to_Long = 180 / self::PI * ($RadLAM0 + $Et * $X - pow($Et, 3) * $XI + pow($Et, 5) * $XII - pow($Et, 7) * $XIIA);
return $E_N_to_Long;
}
