/**
* Function: deriveConstants
* Sets several derived constant values and initialization of datum and ellipse parameters.
*
*/
public function deriveConstants()
{
if (isset($this->nagrids) && $this->nagrids == '@null') {
$this->datumCode = 'none';
}
if (isset($this->datumCode) && $this->datumCode != 'none') {
$datumDef = $this->proj4php->getDatum($this->datumCode);
if (is_array($datumDef)) {
$this->datum_params = array_key_exists('towgs84', $datumDef) ? explode(',', $datumDef['towgs84']) : null;
$this->ellps = $datumDef['ellipse'];
$this->datumName = array_key_exists('name', $datumDef) ? $datumDef['name'] : $this->datumCode;
}
}
// Do we have an ellipsoid?
if (!isset($this->a)) {
if (!isset($this->ellps) || strlen($this->ellps) == 0 || !$this->proj4php->hasEllipsoid($this->ellps)) {
$ellipse = $this->proj4php->getEllipsoid('WGS84');
} else {
$ellipse = $this->proj4php->getEllipsoid($this->ellps);
}
Proj4php::extend($this, $ellipse);
}
if (isset($this->rf) && !isset($this->b)) {
$this->b = (1.0 - 1.0 / $this->rf) * $this->a;
}
if (isset($this->rf) && $this->rf === 0 || abs($this->a - $this->b) < Common::EPSLN) {
$this->sphere = true;
$this->b = $this->a;
}
// used in geocentric
$this->a2 = $this->a * $this->a;
// used in geocentric
$this->b2 = $this->b * $this->b;
// e ^ 2
$this->es = ($this->a2 - $this->b2) / $this->a2;
// eccentricity
$this->e = sqrt($this->es);
if (isset($this->R_A)) {
$this->a *= 1.0 - $this->es * (Common::SIXTH + $this->es * (Common::RA4 + $this->es * Common::RA6));
$this->a2 = $this->a * $this->a;
$this->b2 = $this->b * $this->b;
$this->es = 0.0;
}
// used in geocentric
$this->ep2 = ($this->a2 - $this->b2) / $this->b2;
if (!isset($this->k0)) {
// default value
$this->k0 = 1.0;
}
// DGR 2010-11-12: axis
if (!isset($this->axis)) {
$this->axis = "enu";
}
$this->datum = new Datum($this);
}
