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<?php
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/**
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 * Author : Julien Moquet
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 *
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 * Inspired by Proj4php from Mike Adair madairATdmsolutions.ca
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 *                      and Richard Greenwood rich@greenwoodma$p->com
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 * License: LGPL as per: http://www.gnu.org/copyleft/lesser.html
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 */
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class Proj4phpProjSterea {
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    protected $dependsOn = 'gauss';
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    /**
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     *
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     * @return void
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     */
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    public function init() {
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        if( !$this->rc ) {
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            Proj4php::reportError( "sterea:init:E_ERROR_0" );
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            return;
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        }
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        $this->sinc0 = sin( $this->phic0 );
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        $this->cosc0 = cos( $this->phic0 );
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        $this->R2 = 2.0 * $this->rc;
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        if( !$this->title )
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            $this->title = "Oblique Stereographic Alternative";
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    }
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    /**
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     *
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     * @param type $p
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     * @return type
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     */
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    public function forward( $p ) {
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        $p->x = Proj4php::$common->adjust_lon( $p->x - $this->long0 ); /* adjust del longitude */
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        $p = Proj4php::$proj['gauss']->forward( $p );
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        $sinc = sin( $p->y );
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        $cosc = cos( $p->y );
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        $cosl = cos( $p->x );
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        $k = $this->k0 * $this->R2 / (1.0 + $this->sinc0 * $sinc + $this->cosc0 * $cosc * $cosl);
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        $p->x = $k * $cosc * sin( $p->x );
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        $p->y = $k * ($this->cosc0 * sinc - $this->sinc0 * $cosc * $cosl);
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        $p->x = $this->a * $p->x + $this->x0;
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        $p->y = $this->a * $p->y + $this->y0;
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        return $p;
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    }
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    /**
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     *
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     * @param type $p
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     * @return type
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     */
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    public function inverse( $p ) {
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        #$lon;
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        #$lat;
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        $p->x = ($p->x - $this->x0) / $this->a; /* descale and de-offset */
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        $p->y = ($p->y - $this->y0) / $this->a;
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        $p->x /= $this->k0;
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        $p->y /= $this->k0;
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        if( ($rho = sqrt( $p->x * $p->x + $p->y * $p->y ) ) ) {
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            $c = 2.0 * atan2( $rho, $this->R2 );
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            $sinc = sin( $c );
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            $cosc = cos( $c );
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            $lat = asin( $cosc * $this->sinc0 + $p->y * $sinc * $this->cosc0 / $rho );
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            $lon = atan2( $p->x * $sinc, $rho * $this->cosc0 * $cosc - $p->y * $this->sinc0 * $sinc );
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        } else {
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            $lat = $this->phic0;
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            $lon = 0.;
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        }
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        $p->x = $lon;
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        $p->y = $lat;
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        $p = Proj4php::$proj['gauss']->inverse( $p );
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        $p->x = Proj4php::$common->adjust_lon( $p->x + $this->long0 ); /* adjust longitude to CM */
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        return $p;
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    }
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}
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Proj4php::$proj['sterea'] = new Proj4phpProjSterea();