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| <?php |
| /******************************************************************************* |
| NAME LAMBERT CYLINDRICAL EQUAL AREA |
| |
| PURPOSE: Transforms input longitude and latitude to Easting and |
| Northing for the Lambert Cylindrical Equal Area projection. |
| This class of projection includes the Behrmann and |
| Gall-Peters Projections. The |
| longitude and latitude must be in radians. The Easting |
| and Northing values will be returned in meters. |
| |
| PROGRAMMER DATE |
| ---------- ---- |
| R. Marsden August 2009 |
| Winwaed Software Tech LLC, http://www.winwaed.com |
| |
| This function was adapted from the Miller Cylindrical Projection in the Proj4php |
| library. |
| |
| Note: This implementation assumes a Spherical Earth. The (commented) code |
| has been included for the ellipsoidal forward transform, but derivation of |
| the ellispoidal inverse transform is beyond me. Note that most of the |
| Proj4php implementations do NOT currently support ellipsoidal figures. |
| Therefore this is not seen as a problem - especially this lack of support |
| is explicitly stated here. |
| |
| ALGORITHM REFERENCES |
| |
| 1. "Cartographic Projection Procedures for the UNIX Environment - |
| A User's Manual" by Gerald I. Evenden, USGS Open File Report 90-284 |
| and Release 4 Interim Reports (2003) |
| |
| 2. Snyder, John P., "Flattening the Earth - Two Thousand Years of Map |
| Projections", Univ. Chicago Press, 1993 |
| ****************************************************************************** */ |
| |
| /** |
| * 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 |
| */ |
| class Proj4phpProjCea { |
| /* Initialize the Cylindrical Equal Area projection |
| ------------------------------------------- */ |
| |
| public function init() { |
| //no-op |
| } |
| |
| /* Cylindrical Equal Area forward equations--mapping lat,long to x,y |
| ------------------------------------------------------------ */ |
| public function forward( $p ) { |
| |
| $lon = $p->x; |
| $lat = $p->y; |
| |
| /* Forward equations |
| ----------------- */ |
| $dlon = Proj4php::$common->adjust_lon( $lon - $this->long0 ); |
| $x = $this->x0 + $this->a * $dlon * cos( $this->lat_ts ); |
| $y = $this->y0 + $this->a * sin( $lat ) / cos( $this->lat_ts ); |
| /* Elliptical Forward Transform |
| Not implemented due to a lack of a matchign inverse function |
| { |
| $Sin_Lat = sin(lat); |
| $Rn = $this->a * (sqrt(1.0e0 - $this->es * Sin_Lat * Sin_Lat )); |
| x = $this->x0 + $this->a * dlon * cos($this->lat_ts); |
| y = $this->y0 + Rn * sin(lat) / cos($this->lat_ts); |
| } |
| */ |
| |
| $p->x = $x; |
| $p->y = $y; |
| |
| return $p; |
| } |
| |
| /** |
| * Cylindrical Equal Area inverse equations--mapping x,y to lat/long |
| * |
| * @param type $p |
| * @return type |
| */ |
| public function inverse( $p ) { |
| $p->x -= $this->x0; |
| $p->y -= $this->y0; |
| |
| $p->x = Proj4php::$common->adjust_lon( $this->long0 + ($p->x / $this->a) / cos( $this->lat_ts ) ); |
| $p->y = asin( ($p->y / $this->a) * cos( $this->lat_ts ) ); |
| |
| return $p; |
| } |
| } |
| |
| Proj4php::$proj['cea'] = new Proj4phpProjCea(); |