[mapserver-users] MapScript WMS request

[Mr. Puneet Kishor]

On Sep 9, 2011, at 8:39 AM, Fawcett, David (MPCA) wrote:

> Puneet, 
> 
> As far as I know, OpenLayers still has support for a layer based on MapServer CGI.  Because MapServer can also serve up WMS well, this layer type isn't necessarily recommended or as well supported.  
> 
> http://dev.openlayers.org/docs/files/OpenLayers/Layer/MapServer-js.html



Indeed David. Because, going by the docs, the MapServer CGI calls are discouraged (or so it seems), I'd rather not invest in that path. This is a long term project that I am working on, so the foundations have to be very robust. Besides, I may or may not use OL. While I like OL a lot, I am also looking at other frameworks (Gmaps, Leaflet, Polymaps), and it would be wise to decouple the backend from the front-end as much as possible.

I have no issues with using WMS, but I just am unable to get MapServer WMS to work via MapScript. And, yes, I do have to use MapScript if I can help it -- my layer classification is generated on demand, and MapScript is the easiest way I can think of for doing that.

I did find yesterday that `mode=tile` works really well, but I am trying to make that work with MapScript. A separate email thread for that question.




> 
> David.
> 
> -----Original Message-----
> From: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Mr. Puneet Kishor
> Sent: Thursday, September 08, 2011 9:32 PM
> To: Daniel Morissette
> Cc: mapserver-users at lists.osgeo.org
> Subject: Re: [mapserver-users] MapScript WMS request
> 
> 
> On Sep 8, 2011, at 8:28 PM, Daniel Morissette wrote:
> 
>> On 11-09-08 09:02 PM, Mr. Puneet Kishor wrote:
>>> 
>>> On Sep 8, 2011, at 7:43 PM, Daniel Morissette wrote:
>>>> 
>>>> Maybe call $map->save("/tmp/my.map") in your script after the map and layer have been populated and paste the result... that may give us a hint...
>>>> 
>>> 
>>> wow! this is a super-awesome debugging technique. I have sent you the map file off list to not pollute the entire list serve.
>>> 
>> 
>> I was able to reproduce the issue with the copy of the mapfile you sent off-list.
>> 
>> It turns out that mappostgis.c's msPostGISLayerGetExtent() is hardcoded to always return
>> 
>> {minx = -25000000, miny = -25000000, maxx = 25000000, maxy = 25000000}
>> 
>> ...and then it returns MS_SUCCESS.
>> 
>> I think this function should either be left unimplemented (this way MapServer would fallback on other mechanisms), or return MS_FAILURE to indicate to the calling code that it didn't do anything useful.
>> 
>> A quick search indicates an open ticket about the issue:
>> 
>> http://trac.osgeo.org/mapserver/ticket/3585
>> 
>> You could bump the ticket and hope someone works on it at the FOSS4G code sprint next week.
>> 
>> The short term fix for you would be to set the "ows_extent" metadata in your layer:
>> 
>>   METADATA
>>     "ows_extent" "-180 -90 180 90"
>>  ...
>>   END
>> 
> 
> 
> Thanks Daniel. I will bump the ticket. For now, see below --
> 
> Using the "my.map" file I sent you, with no further modifications to it, I am able to successfully get an image back via [http://localhost.local/cgi-bin/gmna?SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&BBOX=-180,-90,180,90&SRS=EPSG:4326&WIDTH=1200&HEIGHT=600&LAYERS=gmna&STYLES=&FORMAT=image/png&TRANSPARENT=true]
> 
> Note, no further modifications is required, that is, not even the "ows_extent" "-180 -90 180 90" bit in the layer METADATA. and I still get a good image.
> 
> 
> However, if I use the following program to access the same map file, I get the spurious "minx = -25000000, miny = -25000000, maxx = 25000000, maxy = 25000000" in the GetCapabilities.
> 
> Finally, if I add the "ows_extent" "-180 -90 180 90" line in the layer METADATA in the "my.map" file, the GetCapabilities returns the correct bounds now, however, the image is still blank.
> 
> 	#!/opt/local/bin/perl
> 	
> 	use strict;
> 	use mapscript;
> 	
> 	my $wms = new mapscript::OWSRequest();
> 	$wms->setParameter("SERVICE", "WMS" );
> 	$wms->setParameter("VERSION", "1.1.1" );
> 	$wms->setParameter("REQUEST", "GetMap" );
> 	$wms->setParameter("BBOX", "-180,-90,180,90" );
> 	$wms->setParameter("LAYERS", "gmna");
> 	$wms->setParameter("SRS", "EPSG:4326");
> 	$wms->setParameter("WIDTH", "1200");
> 	$wms->setParameter("HEIGHT", "600");
> 	$wms->setParameter("FORMAT", "image/png");
> 	$wms->setParameter("TRANSPARENT", "true");
> 	
> 	my $map = new mapscript::mapObj("/Users/punkish/Sites/test/mapscript/my.map");
> 	
> 	if(!$map) {
> 		warn "New mapObj() error: $mapscript::ms_error->{message}\n";
> 	}
> 	
> 	my $io = mapscript::msIO_installStdoutToBuffer();
> 	my $dispatch_out = $map->OWSDispatch( $wms );
> 	printf "%s\n", mapscript::msIO_getStdoutBufferString();
> 
> I have now spent an enormous amount of time on this, and for now, I have to move on. This is just not working out. Maybe I will try some other technique, perhaps this mode=tile to see if I can get MapServer powered maps in my apps.
> 
> Thanks much for your help. If you (or anyone else) can come up with a bright idea, I will be happy to try it.
> 
> Puneet.
> 
> _______________________________________________
> mapserver-users mailing list
> mapserver-users at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/mapserver-users
> 
>