Mapscript Re-Projection on-the-fly

[Delfos, Jacob]

Hi Stefan,
 
Yes, you do have to specify which projection each layer is in, otherwise
when they are reprojected you will run into trouble (if it doesn't know
where to reproject FROM, it won't be able to do i). It's not too hard,
though. 
 
You should not have to recalculate the extent; it should be automatic.
Definitely don't try to change the numbers (coordinates) without
changing the projection (that would be bad).
 
Try this:
 
$newproj="proj=robin,lon_0=0,x_0=0,y_0=0"; // projection string of your
new projection
$map->setProjection($newproj,MS_TRUE);
 
I think that ought to be all.  The MS_TRUE makes it pick the best fit to
the current extent in the new projection. Make sure your projection
string is valid.
 
regards,
 
Jacob
 
 


________________________________

	From: UMN MapServer Users List
[mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On Behalf Of Stefan Schwarzer
	Sent: 24 August 2006 15:35
	To: MAPSERVER-USERS at LISTS.UMN.EDU
	Subject: Re: [UMN_MAPSERVER-USERS] Mapscript Re-Projection
on-the-fly
	
	
	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_def
s");
	$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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