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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                            MERCATOR
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  PURPOSE:	Transforms input longitude and latitude to Easting and
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  Northing for the Mercator projection.  The
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  longitude and latitude must be in radians.  The Easting
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  and Northing values will be returned in meters.
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  PROGRAMMER              DATE
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  ----------              ----
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  D. Steinwand, EROS      Nov, 1991
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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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//static double r_major = a;		   /* major axis 				*/
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//static double r_minor = b;		   /* minor axis 				*/
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//static double lon_center = long0;	   /* Center longitude (projection center) */
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//static double lat_origin =  lat0;	   /* center latitude			*/
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//static double e,es;		           /* eccentricity constants		*/
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//static double m1;		               /* small value m			*/
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//static double false_northing = y0;   /* y offset in meters			*/
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//static double false_easting = x0;	   /* x offset in meters			*/
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//scale_fact = k0
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class Proj4phpProjMerc {
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    public function init() {
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        //?$this->temp = $this->r_minor / $this->r_major;
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        //$this->temp = $this->b / $this->a;
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        //$this->es = 1.0 - sqrt($this->temp);
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        //$this->e = sqrt( $this->es );
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        //?$this->m1 = cos($this->lat_origin) / (sqrt( 1.0 - $this->es * sin($this->lat_origin) * sin($this->lat_origin)));
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        //$this->m1 = cos(0.0) / (sqrt( 1.0 - $this->es * sin(0.0) * sin(0.0)));
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        if( $this->lat_ts ) {
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            if( $this->sphere ) {
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                $this->k0 = cos( $this->lat_ts );
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            } else {
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                $this->k0 = Proj4php::$common->msfnz( $this->es, sin( $this->lat_ts ), cos( $this->lat_ts ) );
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            }
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        }
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    }
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    /* Mercator forward equations--mapping lat,long to x,y
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      -------------------------------------------------- */
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    public function forward( $p ) {
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        //alert("ll2m coords : ".coords);
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        $lon = $p->x;
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        $lat = $p->y;
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        // convert to radians
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        if( $lat * Proj4php::$common->R2D > 90.0 &&
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                  $lat * Proj4php::$common->R2D < -90.0 &&
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                  $lon * Proj4php::$common->R2D > 180.0 &&
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                  $lon * Proj4php::$common->R2D < -180.0 ) {
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            Proj4php::reportError( "merc:forward: llInputOutOfRange: " . $lon . " : " . $lat );
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            return null;
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        }
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        if( abs( abs( $lat ) - Proj4php::$common->HALF_PI ) <= Proj4php::$common->EPSLN ) {
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            Proj4php::reportError( "merc:forward: ll2mAtPoles" );
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            return null;
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        } else {
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            if( $this->sphere ) {
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                $x = $this->x0 + $this->a * $this->k0 * Proj4php::$common->adjust_lon( $lon - $this->long0 );
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                $y = $this->y0 + $this->a * $this->k0 * log( tan( Proj4php::$common->FORTPI + 0.5 * $lat ) );
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            } else {
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                $sinphi = sin( lat );
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                $ts = Proj4php::$common . tsfnz( $this->e, $lat, $sinphi );
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                $x = $this->x0 + $this->a * $this->k0 * Proj4php::$common->adjust_lon( $lon - $this->long0 );
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                $y = $this->y0 - $this->a * $this->k0 * log( $ts );
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            }
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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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    }
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    /* Mercator inverse equations--mapping x,y to lat/long
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      -------------------------------------------------- */
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    public function inverse( $p ) {
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        $x = $p->x - $this->x0;
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        $y = $p->y - $this->y0;
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        if( $this->sphere ) {
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            $lat = Proj4php::$common->HALF_PI - 2.0 * atan( exp( -$y / $this->a * $this->k0 ) );
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        } else {
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            $ts = exp( -$y / ($this->a * $this->k0) );
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            $lat = Proj4php::$common->phi2z( $this->e, $ts );
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            if( $lat == -9999 ) {
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                Proj4php::reportError( "merc:inverse: lat = -9999" );
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                return null;
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            }
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        }
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        $lon = Proj4php::$common->adjust_lon( $this->long0 + $x / ($this->a * $this->k0) );
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        $p->x = $lon;
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        $p->y = $lat;
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        return $p;
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    }
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}
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Proj4php::$proj['merc'] = new Proj4phpProjMerc();
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