Mapscript Re-Projection on-the-fly

[Stefan Schwarzer]

Jacob & Nicol,

thanks for your feedback.

But I am still struggling. Just to clarify: I wonna reproject not  
individual layers, but my whole map.

Jacob, does "For this, it is required that your layer has a  
projection object with the native projection of that layer." that  
mean that for each single layer I have to specify the original  
projection? (Geographic in my case)

As Nicol stated I need to "recalculate" the extent, at least when  
using different units (going from DD to Meters).

But then, I found that piece of code (slightly changed):

	$newproj=ms_newprojectionObj("proj=robin,lon_0=0,x_0=0,y_0=0");
	$latlon=ms_newprojectionObj 
("proj=longlat,ellps=WGS84,datum=WGS84,no_defs");
	$oldext=ms_newRectObj();
	$oldext->setextent(-180,-90,180,90);  //this is the extent of my map  
in geographic
	$oldext->project($latlon,$newproj);  //reproject to Robinson
	$map->setextent($oldext->minx,$oldext->miny,$oldext->maxx,$oldext- 
 >maxy);  //set the new map extent

And another one going like this:

	$projInObj = ms_newProjectionObj( "+proj=tmerc ".
	  "+lat_0=49 ".
	  "+lon_0=-2 ".
	  "+k=0.999601 ".
	  "+x_0=400000 ".
	  "+y_0=-100000 ".
	  "+ellps=airy ".
	  "+towgs84=375,-111,431,0,0,0,0");

with this info in the mapscript documentation...
	 int setProjection(string proj_params, boolean bSetUnitsAndExtents)
         Set map projection and coordinate system.  Parameters are  
given as
         a single string of comma-delimited PROJ.4 parameters.
         The argument : bSetUnitsAndExtents is used to automatically  
update
         the map units and extents based on the new projection. Possible
         values are MS_TRUE and MS_FALSE. By defualt it is set at  
MS_FALSE

So, what should I use? And where is coming the 	

	$map -> setProjection

into play?

Thanks for any clarification.

Stefan



On Aug 24, 2006, at 7:59 AM, Delfos, Jacob wrote:

> Stefan,
>
> Your question is not entirely clear. You can not re-project an  
> individual layer on-the-fly, because php_mapscript does not re- 
> write the dataset (hence its projection will always be the same);  
> you CAN however change the projection of the map (using  
> setProjection, as you did), which means all layers in the map get  
> re-projected (the dataset remains unchanged, though). For this, it  
> is required that your layer has a projection object with the native  
> projection of that layer. This will cause the layer to be  
> reprojected along with the map. Is this what you are trying to do?
>
> You *may* have to save your mapfile, or your session, in order for  
> it to take effect, depending on your setup.
>
> regards,
>
> Jacob
>
>
> From: UMN MapServer Users List [mailto:MAPSERVER- 
> USERS at LISTS.UMN.EDU] On Behalf Of Stefan Schwarzer
> Sent: 24 August 2006 13:45
> To: MAPSERVER-USERS at LISTS.UMN.EDU
> Subject: Re: [UMN_MAPSERVER-USERS] Mapscript Re-Projection on-the-fly
>
> Hey,
>
> I can't imagine that such a question stays unanswered in the  
> mapserver community...
>
> I meanwhile added a:
>
> $map -> setProjection("init=epsg:26711");
>
> to my code, but nothing happens - meaning: no error message but no  
> reprojection either.
>
> Can anyone help me out?
>
> Thanks in advance.
>
> Stefan
>
>
> On Aug 22, 2006, at 10:47 AM, Stefan Schwarzer wrote:
>
>> Gush,
>>
>> I couldn't find any precise information about how to re-project  
>> layers on-the-fly via PHP Mapscript. Here and there (via  
>> MailingList and Google) bits and pieces, but altogether it didn't  
>> help me a lot. Though I would have said that this is a basic  
>> question. But perhaps too basic, so everbody finds out by himself?
>>
>> So, can anyone let me know - giving a coding example - how to re- 
>> project a mapfile on-the-fly from for example Lat/Long (global  
>> view) to Lambert or Robin?
>>
>> Thanks a lot for your help!
>>
>>
>

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