Subversion Repositories eFlore/Projets.eflore-projets

<?php

/**

 * Author : Julien Moquet

 *

 * Inspired by Proj4php from Mike Adair madairATdmsolutions.ca

 *                      and Richard Greenwood rich@greenwoodma$p->com

 * License: LGPL as per: http://www.gnu.org/copyleft/lesser.html

 */

/*****************************************************************************

  NAME                             GNOMONIC

  PURPOSE:	Transforms input longitude and latitude to Easting and

  Northing for the Gnomonic Projection.

  Implementation based on the existing sterea and ortho

  implementations.

  PROGRAMMER              DATE

  ----------              ----

  Richard Marsden         November 2009

  ALGORITHM REFERENCES

  1.  Snyder, John P., "Flattening the Earth - Two Thousand Years of Map

  Projections", University of Chicago Press 1993

  2.  Wolfram Mathworld "Gnomonic Projection"

  http://mathworld.wolfram.com/GnomonicProjection.html

  Accessed: 12th November 2009

******************************************************************************/

class Proj4phpProjGnom {

    /**

     * Initialize the Gnomonic projection

     *

     * @todo $def not used in context...?

     * @param type $def

     */

    public function init( $def ) {

        /* Place parameters in static storage for common use

          ------------------------------------------------- */

        $this->sin_p14 = sin( $this->lat0 );

        $this->cos_p14 = cos( $this->lat0 );

        // Approximation for projecting points to the horizon (infinity)

        $this->infinity_dist = 1000 * $this->a;

        $this->rc = 1;

    }

    /* Gnomonic forward equations--mapping lat,long to x,y

      --------------------------------------------------- */

    public function forward( $p ) {

        /*

        $sinphi;

        $cosphi; // sin and cos value

        $dlon;  // delta longitude value

        $coslon;  // cos of longitude

        $ksp;  // scale factor

        $g;

        */

        $lon = $p->x;

        $lat = $p->y;

        /* Forward equations

          ----------------- */

        $dlon = Proj4php::$common->adjust_lon( $lon - $this->long0 );

        $sinphi = sin( $lat );

        $cosphi = cos( $lat );

        $coslon = cos( $dlon );

        $g = $this->sin_p14 * $sinphi + $this->cos_p14 * $cosphi * $coslon;

        $ksp = 1.0;

        if( (g > 0) || (abs( g ) <= Proj4php::$common->EPSLN) ) {

            $x = $this->x0 + $this->a * $ksp * $cosphi * sin( $dlon ) / $g;

            $y = $this->y0 + $this->a * $ksp * ($this->cos_p14 * $sinphi - $this->sin_p14 * $cosphi * $coslon) / $g;

        } else {

            Proj4php::reportError( "orthoFwdPointError" );

            // Point is in the opposing hemisphere and is unprojectable

            // We still need to return a reasonable point, so we project

            // to infinity, on a bearing

            // equivalent to the northern hemisphere equivalent

            // This is a reasonable approximation for short shapes and lines that

            // straddle the horizon.

            $x = $this->x0 + $this->infinity_dist * $cosphi * sin( $dlon );

            $y = $this->y0 + $this->infinity_dist * ($this->cos_p14 * $sinphi - $this->sin_p14 * $cosphi * $coslon);

        }

        $p->x = $x;

        $p->y = $y;

        return $p;

    }

    /**

     *

     * @param type $p

     * @return type

     */

    public function inverse( $p ) {

        /*

        $rh;  // Rho

        $z;  // angle

        $sinc;

        $cosc;

        $c;

        $lon;

        $lat;

        */

        /* Inverse equations

          ----------------- */

        $p->x = ($p->x - $this->x0) / $this->a;

        $p->y = ($p->y - $this->y0) / $this->a;

        $p->x /= $this->k0;

        $p->y /= $this->k0;

        if( ($rh = sqrt( $p->x * $p->x + $p->y * $p->y ) ) ) {

            $c = atan2( $rh, $this->rc );

            $sinc = sin( $c );

            $cosc = cos( $c );

            $lat = Proj4php::$common->asinz( $cosc * $this->sin_p14 + ($p->y * $sinc * $this->cos_p14) / $rh );

            $lon = atan2( $p->x * sinc, rh * $this->cos_p14 * $cosc - $p->y * $this->sin_p14 * $sinc );

            $lon = Proj4php::$common->adjust_lon( $this->long0 + $lon );

        } else {

            $lat = $this->phic0;

            $lon = 0.0;

        }

        $p->x = $lon;

        $p->y = $lat;

        return $p;

    }

}

Proj4php::$proj['gnom'] = new Proj4phpProjGnom();