[OpenLayers-Users] MapServer Layer for ECW creating blank tiles

[Christopher Schmidt]

On Wed, Jun 17, 2009 at 06:53:13AM -0700, soatley wrote:
> 
> Hopefully someone with some Mapserver knowledge can help me out as I am
> having problems getting Mapserver to work with OL.
> 
> First a little background.  I have OL 2.8 rc6 up and running with multiple
> layers being pulled via my WMS server (Manifold).  I have been having
> problems getting Manifold to generate the tiles for ECW files so I am
> turning to MapServer to hopefully solve the problem.  I am not a GIS person,
> I am a web programmer, so please go easy.
> 
> Here is the output of gdalinfo on my ECW File:
> 
> Driver: ECW/ERMapper Compressed Wavelets
> Files: ortho.ecw
> Size is 75010, 115010
> Coordinate System is:
> PROJCS["NUTM17",
>     GEOGCS["NAD83",
>         DATUM["North_American_Datum_1983",
>             SPHEROID["GRS 1980",6378137,298.257222101,
>                 AUTHORITY["EPSG","7019"]],
>             TOWGS84[0,0,0,0,0,0,0],
>             AUTHORITY["EPSG","6269"]],
>         PRIMEM["Greenwich",0,
>             AUTHORITY["EPSG","8901"]],
>         UNIT["degree",0.0174532925199433,
>             AUTHORITY["EPSG","9108"]],
>         AXIS["Lat",NORTH],
>         AXIS["Long",EAST],
>         AUTHORITY["EPSG","4269"]],
>     PROJECTION["Transverse_Mercator"],
>     PARAMETER["latitude_of_origin",0],
>     PARAMETER["central_meridian",-81],
>     PARAMETER["scale_factor",0.9996],
>     PARAMETER["false_easting",500000],
>     PARAMETER["false_northing",0],
>     UNIT["Meter",1]]
> Origin = (646999.000000000000000,4780000.999999986000000)
> Pixel Size = (0.200000000000000,-0.200000000000000)
> Corner Coordinates:
> Upper Left  (  646999.000, 4780001.000) ( 79d11'30.77"W, 43d 9'30.53"N)
> Lower Left  (  646999.000, 4756999.000) ( 79d11'52.64"W, 42d57'5.23"N)
> Upper Right (  662001.000, 4780001.000) ( 79d 0'26.85"W, 43d 9'19.50"N)
> Lower Right (  662001.000, 4756999.000) ( 79d 0'50.94"W, 42d56'54.27"N)
> Center      (  654500.000, 4768500.000) ( 79d 6'10.32"W, 43d 3'12.52"N)
> Band 1 Block=75010x1 Type=Byte, ColorInterp=Red
>   Overviews: arbitrary
> Band 2 Block=75010x1 Type=Byte, ColorInterp=Green
>   Overviews: arbitrary
> Band 3 Block=75010x1 Type=Byte, ColorInterp=Blue
>   Overviews: arbitrary
> 
> 
> Viewing some documentation and using google, I created this map file:
> 
> MAP
> 	PROJECTION  "init=epsg:4326"
> 	END
> 
> 	SIZE 256 256
> 	STATUS ON
> 	EXTENT 646999.000 4756999.000 662001.000 4780001.000
> 
> 	UNITS METERS
> 
> 
> 	LAYER
> 	    NAME "orthoEnhanced"
> 	    TYPE RASTER
> 	    STATUS ON
> 	    PROJECTION "init=epsg:4326"
> 	    END
> 	
> 	    DATA "O:\ortho.ecw"
> 	    
> 	    
> 	    CLASS
> 	        STYLE
> 	            COLOR 110 50 100
> 	            OUTLINECOLOR 200 200 200
> 	            SYMBOL 0
> 	        END
> 	    END
> 	END 
> END
> 
> 
> And then created the layer for OpenLayers:
> 
>     var msecw = new OpenLayers.Layer.MapServer("OpenLayers WMS",
>                     "http://127.0.0.1:81/cgi-bin/mapserv.exe?map=ecw.map", {
> layers: 'orthoEnhanced' });
> 
>     map.addLayer(msecw);

Instead of using a MapServer layer, instead add the following to your
mapfile:

  web
    metadata
      wms_srs "EPSG:4326"
    end
  end

If your OpenLayers Map is in a different projection, use
EPSG:ThatProjection instead.  

Then, change "MapServer" above to "WMS" (nothing else) and see where you
can get. I think you're likely dealing with a projection issue, and the
WMS layer will make it easier to debug.

-- Chris

> 
> All of my tiles are coming blank.  Here is what Firebug says for the
> MapServer requests:
> 
> http://127.0.0.1:81/cgi-bin/mapserv.exe?map=ecw.map&layers=orthoEnhanced&mode=map&map_imagetype=png&mapext=-79.162519+42.920835+-79.100019+42.983335&imgext=-79.162519+42.920835+-79.100019+42.983335&map_size=256+256&imgx=128&imgy=128&imgxy=256+256
> 
> 
> One thing I can see is that my extents in the request are Lat Long and the
> Extents in the Map file are UTM 17.  Should the map file be changed to Lat
> Long? (And how do I convert the values)
> 
> If I were to hack around on the Mapserv.exe url, and remove everything in
> the querystring except the following:
> 
> http://127.0.0.1:81/cgi-bin/mapserv.exe?map=ecw.map&mode=map&map_imagetype=png&layers=orthoEnhanced
> 
> 
> then I get a picture of the full ortho.  In my mind, that means that
> MapServer can read the ecw file and generate a 256X256 PNG.  
> 
> Once I append the coordinates that url, then I just get blank tiles.
> 
> Any help would be greatly appreciated!!!
> 
> Thanks,
> Shawn
> -- 
> View this message in context: http://n2.nabble.com/MapServer-Layer-for-ECW-creating-blank-tiles-tp3092922p3092922.html
> Sent from the OpenLayers Users mailing list archive at Nabble.com.
> 
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