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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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/*******************************************************************************
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  NAME                            EQUIDISTANT CONIC
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  PURPOSE:	Transforms input longitude and latitude to Easting and Northing
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  for the Equidistant Conic projection.  The longitude and
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  latitude must be in radians.  The Easting and Northing values
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  will be returned in meters.
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  PROGRAMMER              DATE
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  ----------              ----
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  T. Mittan		Mar, 1993
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  ALGORITHM REFERENCES
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  1.  Snyder, John $p->, "Map Projections--A Working Manual", U.S. Geological
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  Survey Professional Paper 1395 (Supersedes USGS Bulletin 1532), United
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  State Government Printing Office, Washington D.C., 1987.
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  2.  Snyder, John $p-> and Voxland, Philip M., "An Album of Map Projections",
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  U.S. Geological Survey Professional Paper 1453 , United State Government
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  Printing Office, Washington D.C., 1989.
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*******************************************************************************/
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/* Variables common to all subroutines in this code file
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-----------------------------------------------------*/
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class Proj4phpProjEqdc {
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    /* Initialize the Equidistant Conic projection
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      ------------------------------------------ */
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    public function init() {
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        /* Place parameters in static storage for common use
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          ------------------------------------------------- */
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        if( !$this->mode )
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            $this->mode = 0; //chosen default mode
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        $this->temp = $this->b / $this->a;
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        $this->es = 1.0 - pow( $this->temp, 2 );
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        $this->e = sqrt( $this->es );
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        $this->e0 = Proj4php::$common->e0fn( $this->es );
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        $this->e1 = Proj4php::$common->e1fn( $this->es );
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        $this->e2 = Proj4php::$common->e2fn( $this->es );
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        $this->e3 = Proj4php::$common->e3fn( $this->es );
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        $this->sinphi = sin( $this->lat1 );
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        $this->cosphi = cos( $this->lat1 );
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        $this->ms1 = Proj4php::$common->msfnz( $this->e, $this->sinphi, $this->cosphi );
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        $this->ml1 = Proj4php::$common->mlfn( $this->e0, $this->e1, $this->e2, $this->e3, $this->lat1 );
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        /* format B
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          --------- */
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        if( $this->mode != 0 ) {
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            if( abs( $this->lat1 + $this->lat2 ) < Proj4php::$common->EPSLN ) {
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                Proj4php::reportError( "eqdc:Init:EqualLatitudes" );
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                //return(81);
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            }
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            $this->sinphi = sin( $this->lat2 );
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            $this->cosphi = cos( $this->lat2 );
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            $this->ms2 = Proj4php::$common->msfnz( $this->e, $this->sinphi, $this->cosphi );
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            $this->ml2 = Proj4php::$common->mlfn( $this->e0, $this->e1, $this->e2, $this->e3, $this->lat2 );
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            if( abs( $this->lat1 - $this->lat2 ) >= Proj4php::$common->EPSLN ) {
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                $this->ns = ($this->ms1 - $this->ms2) / ($this->ml2 - $this->ml1);
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            } else {
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                $this->ns = $this->sinphi;
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            }
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        } else {
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            $this->ns = $this->sinphi;
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        }
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        $this->g = $this->ml1 + $this->ms1 / $this->ns;
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        $this->ml0 = Proj4php::$common->mlfn( $this->e0, $this->e1, $this->e2, $this->e3, $this->lat0 );
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        $this->rh = $this->a * ($this->g - $this->ml0);
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    }
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    /* Equidistant Conic forward equations--mapping lat,long to x,y
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      ----------------------------------------------------------- */
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    public function forward( $p ) {
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        $lon = $p->x;
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        $lat = $p->y;
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        /* Forward equations
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          ----------------- */
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        $ml = Proj4php::$common->mlfn( $this->e0, $this->e1, $this->e2, $this->e3, $lat );
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        $rh1 = $this->a * ($this->g - $ml);
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        $theta = $this->ns * Proj4php::$common->adjust_lon( $lon - $this->long0 );
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        $x = $this->x0 + $rh1 * sin( $theta );
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        $y = $this->y0 + $this->rh - $rh1 * cos( $theta );
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        $p->x = $x;
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        $p->y = $y;
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        return $p;
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    }
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    /* Inverse equations
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      ----------------- */
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    public function inverse( $p ) {
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        $p->x -= $this->x0;
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        $p->y = $this->rh - $p->y + $this->y0;
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        if( $this->ns >= 0 ) {
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            $rh1 = sqrt( $p->x * $p->x + $p->y * $p->y );
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            $con = 1.0;
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        } else {
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            $rh1 = -sqrt( $p->x * $p->x + $p->y * $p->y );
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            $con = -1.0;
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        }
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        $theta = 0.0;
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        if( $rh1 != 0.0 )
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            $theta = atan2( $con * $p->x, $con * $p->y );
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        $ml = $this->g - $rh1 / $this->a;
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        $lat = $this->phi3z( $ml, $this->e0, $this->e1, $this->e2, $this->e3 );
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        $lon = Proj4php::$common->adjust_lon( $this->long0 + $theta / $this->ns );
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        $p->x = $lon;
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        $p->y = $lat;
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        return $p;
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    }
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    /* Function to compute latitude, phi3, for the inverse of the Equidistant
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      Conic projection.
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      ----------------------------------------------------------------- */
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    public function phi3z( $ml, $e0, $e1, $e2, $e3 ) {
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        $phi = $ml;
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        for( $i = 0; $i < 15; $i++ ) {
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            $dphi = ($ml + $e1 * sin( 2.0 * $phi ) - $e2 * sin( 4.0 * $phi ) + $e3 * sin( 6.0 * $phi )) / $e0 - $phi;
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            $phi += $dphi;
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            if( abs( $dphi ) <= .0000000001 ) {
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                return $phi;
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            }
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        }
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        Proj4php::reportError( "PHI3Z-CONV:Latitude failed to converge after 15 iterations" );
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        return null;
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    }
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}
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Proj4php::$proj['eqdc'] = new Proj4phpProjEqdc();