public function inverse($p)
{
#$con, $phi; /* temporary angles */
#$delta_phi; /* difference between longitudes */
$max_iter = 6;
/* maximun number of iterations */
if ($this->sphere) {
/* spherical form */
$f = exp($p->x / ($this->a * $this->k0));
$g = 0.5 * ($f - 1 / $f);
$temp = $this->lat0 + $p->y / ($this->a * $this->k0);
$h = cos($temp);
$con = sqrt((1.0 - $h * $h) / (1.0 + $g * $g));
$lat = Sourcemap_Proj::asinz($con);
if ($temp < 0) {
$lat = -$lat;
}
if ($g == 0 && $h == 0) {
$lon = $this->long0;
} else {
$lon = Sourcemap_Proj::adjust_lon(atan2($g, $h) + $this->long0);
}
} else {
// ellipsoidal form
$x = $p->x - $this->x0;
$y = $p->y - $this->y0;
$con = ($this->ml0 + $y / $this->k0) / $this->a;
$phi = $con;
for ($i = 0; true; $i++) {
$delta_phi = ($con + $this->e1 * sin(2.0 * $phi) - $this->e2 * sin(4.0 * $phi) + $this->e3 * sin(6.0 * $phi)) / $this->e0 - $phi;
$phi += $delta_phi;
if (abs($delta_phi) <= Sourcemap_Proj::EPSLN) {
break;
}
if ($i >= $max_iter) {
throw new Exception("Latitude failed to converge.");
#return(95);
}
}
if (abs($phi) < Sourcemap_Proj::HALF_PI) {
// sincos(phi, &sin_phi, &cos_phi);
$sin_phi = sin($phi);
$cos_phi = cos($phi);
$tan_phi = tan($phi);
$c = $this->ep2 * pow($cos_phi, 2);
$cs = pow($c, 2);
$t = pow($tan_phi, 2);
$ts = pow($t, 2);
$con = 1.0 - $this->es * pow($sin_phi, 2);
$n = $this->a / sqrt($con);
$r = $n * (1.0 - $this->es) / $con;
$d = $x / ($n * $this->k0);
$ds = pow($d, 2);
$lat = $phi - $n * $tan_phi * $ds / $r * (0.5 - $ds / 24.0 * (5.0 + 3.0 * $t + 10.0 * $c - 4.0 * $cs - 9.0 * $this->ep2 - $ds / 30.0 * (61.0 + 90.0 * $t + 298.0 * $c + 45.0 * $ts - 252.0 * $this->ep2 - 3.0 * $cs)));
$lon = Sourcemap_Proj::adjust_lon($this->long0 + $d * (1.0 - $ds / 6.0 * (1.0 + 2.0 * $t + $c - $ds / 20.0 * (5.0 - 2.0 * $c + 28.0 * $t - 3.0 * $cs + 8.0 * $this->ep2 + 24.0 * $ts))) / $cos_phi);
} else {
$lat = Sourcemap_Proj::HALF_PI * Sourcemap_Proj::sign($y);
$lon = $this->long0;
}
}
$p->x = $lon;
$p->y = $lat;
return $p;
}
