Google maps & Mapserver projection issue

[Jan Hartmann]

With Mapscript it's easy:

function ll2merc($lon,$lat) {
	$projIn = ms_newprojectionobj("proj=latlong");
	$projOut = ms_newprojectionobj("proj=merc");
	$p = ms_newpointobj();
	$p->setXY($lon,$lat);
	$p->project($projIn, $projOut);
	return($p);
}

If you don't use Mapscript, you have to do the computations in 
Javascript. There is a project to implement the Proj package in Javascript:

http://lists.maptools.org/pipermail/proj/2006-February/002125.html

but I have never worked with it

Jan

Jose Olcese wrote:
> Hi Jan,
> 
> I really appreciate your help!. It seems that it might be the problem!.
> I'll try sending Mercator Coordinates in meters as the mapexp parameter 
> of mapserv.
> 
> Do you have the algorithm for converting it?
> 
> Thanks again
> Jose
> 
> 
> 
> 
> On 6/4/07, *Jan Hartmann* < j.l.h.hartmann at uva.nl 
> <mailto:j.l.h.hartmann at uva.nl>> wrote:
> 
>     Hi Jose
> 
>     Epsg 54004 is the classic Mercator projection. The units it uses are not
>     degrees but meters (only at the equator these are real meters). Using
>     proj I get the following boundary values (note that -180W/-90S and
>     180E/90N cannot be represented in a Mercator projection):
> 
>     proj +init=epsg:54004
>     -170 -80
>     -18924313.43    -15496570.74
>     170 80
>     18924313.43     15496570.74
> 
>     Hope this helps,
> 
>     Jan
> 
>     Dr. J. Hartmann
>     Department of Geography
>     University of Amsterdam
> 
>     joseolcese wrote:
>      > Hi
>      >
>      > I'm trying to use Google maps & Mapserver with partial success...
>      > I have a .shp configured in mapserver and I can get a transparent
>     tile from
>      > an html page where it load google satellite view and my tiles.
>      > The problem is that I wasn't using any projection on my .map so
>     every tile
>      > was a little distorted.
>      > I added the epsg:54004 project to the .map but now the tiles are
>     empty.
>      >
>      > Do you have any idea why this my be happening?
>      >
>      > Thanks
>      > Jose Olcese
>      >
>      > .map:
>      >  IMAGETYPE      PNG
>      >  EXTENT           -64.20 -31.41 -64.19 -31.40
>      >  SIZE               256 256
>      >  SHAPEPATH      '/ms4w/apps/tutorial/data_jose'
>      >  FONTSET         '/ms4w/apps/tutorial/fonts/fonts.list'
>      >  TRANSPARENT  ON
>      >  CONFIG PROJ_LIB '/var/www/html/share/proj/'
>      >  PROJECTION
>      >  "init=esri:54004"
>      >  END
>      >   LAYER
>      > ...
>      > ...
>      >
>      >
>      > .html:
>      > ...
>      > ...
>      >         tileCountry.getTileUrl=function(xy,zoom)
>      >         {
>      >             var lng = (-180+((xy.x+0.5)*(360/Math.pow(2,zoom))));
>     // -180
>      > +180
>      >
>      >             var merclat_extent = 360/Math.pow(2,zoom);
>      >             var l = 180 - (( xy.y+0.5) * merclat_extent);
>      >             var e = Math.exp(2 * ( l * Math.PI) /180);
>      >             e = (e - 1)/(e + 1);
>      >             var lat = (Math.atan2(e, Math.sqrt(1 - (e * e))) *180 /
>      > Math.PI );
>      >
>      >             return
>      > '
>     http://127.0.0.1/cgi-bin/mapserv?map=/ms4w/apps/tutorial/htdocs/map_test5.map&mode=map&mapxy=
>     <http://127.0.0.1/cgi-bin/mapserv?map=/ms4w/apps/tutorial/htdocs/map_test5.map&mode=map&mapxy=>'
>      > + lng + '+' + lat + '&buffer=' + ((360/Math.pow(2,zoom))/2);
>      >     }
>      > ...
>      >
>      >
>      >
> 
>