PROJ4, PHP and projection of a single point

[Assefa Yewondwossen]

Hi There,

 I am assuming here that you use php/mapscript.

 There is a php/proj module available in the mapserver distribution (.../mapserver/mapscript/php3/php_proj.c).  This module give access to basic Proj4 fonctionalities. So in
your case you colud use the functions to convert the Georeferenced coordinated to Lat/Long coordinates.

Are you building mapserver/mapscrtipt yourself or do you download the binary versions ? Which platform are you on ? I am asking this so I could post the binary versions on our
download site.

Later,


PS :

Here is a little bit of docs on how to use it :

   /*
 *         PHP PROJ4 Module
 *
 *  This is a PHP module that gives acces to basic PROJ4 projection
 *  functionalities.
 *
 * There are four functions available in this module :
 *
 * 1) pj_init : create and initializes a projection structures
 *
 *    PJ pj_init(array_of_parameters)
 *
 *    Example : $projarray[0] = "proj=lcc";
 *              $projarray[1] = "ellps=GRS80";
 *              $projarray[2] = "lat_0=49";
 *              $projarray[3] = "lon_0=-95";
 *              $projarray[4] = "lat_1=49";
 *              $projarray[5] = "lat_2=77";
 *
 *              $pj = pj_init($projarray);
 *
 * 2) pj_fwd : Performs a projection from lat/long coordinates to
 *             cartesian coordinates.
 *
 * retrun_array pj_fwd(double lat, double long, PJ pj)
 *
 *   Example :  $lat = 45.25;
 *              $long = -75.42;
 *
 *              $ret = pj_fwd($ingeox, $ingeoy, $pj);
 *              printf("geo x = %f<br>\n", $ret["u"]);
 *              printf("geo y = %f<br>\n",$ret["v"]);
 *
 * 3) pj_inv : Performs a projection from cartesian coordinates to
 *             lat/long  coordinates .
 *
 * retrun_array pj_fwd(double geox, double geoy, PJ pj)
 *
 *   Example :  $ingeox = 1537490.335842;
 *              $ingeoy = -181633.471555;
 *
 *              $ret = pj_inv($ingeox, $ingeoy, $pj);
 *              printf("lat = %f<br>\n", $ret["u"]);
 *              printf("lon = %f<br>\n",$ret["v"]);
 *
 * 4) pj_free : frees PJ structure
 *
 *  void pj_free(PJ pj);
 *
 **********************************************************************/


Stephen Lime wrote:

> The solution with MapScript and scripting languages is to use the proj4 modules written first by
> be and a better version was recently posted to the mailing list. Perhaps the folks at DMSolutions
> could dicuss how to create a php/proj module.
>
> Steve
>
> Stephen Lime
> Internet Applications Analyst
>
> Minnesota DNR
> 500 Lafayette Road
> St. Paul, MN 55155
> 651-297-2937
>
> >>> "Stein Runar Bergheim" <runar at bergheim.dk> 02/22/01 03:05AM >>>
> I am retreiving a set of points from a database, and am drawing them onto the image object of a map via a layer that is projected from lat/long to WGS84 coordinates.
>
> This is easy going, my problem occurs when I want to collect a pair of coordinates from the map, perform an inverse projection of them and use them to query the database...
>
> Is this possible or should I try some alternate approach...
>
> Regards
> SRB

--
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Assefa Yewondwossen
Software Analyst

Email: assefa at dmsolutions.ca
http://www.dmsolutions.ca/

Phone: (613) 565-5056
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