[mapserver-users] Does Mapserver WCS 1.0.0 respect OFFSITE of tileindex layer?

[Armin Burger]

Hello Jukka

your assumption how the the OFFSITE tag is applied for the WCS output is 
also what I would have expected it to do. I probably did not notice this 
strange behaviour since my set ups of WCS only used non-overlapping 
tiles (for WMS I use overlapping tiles and the OFFSITE works fine).

Just an idea (I never tried it): maybe you could try to use a VRT image 
instead of the tileindex. At least since Gdal 1.7 there is the tool 
"gdalbuildvrt" that has the options "-srcnodata" and "-vrtnodata" which 
might do what you want.

All tests I made so far with VRT images worked quite fine, they were 
exactly treated as a single image. I don't know if the speed might be a 
bit slower, but WCS is typically slow anyway, so it should not cause 
problems.

Greetings
Armin

On 19/04/2010 16:10, Rahkonen Jukka wrote:
> Frank Warmerdam wrote:
>
>> Jukka,
>>
>> Generally WCS generated geotiffs will not have a way to
>> represent nodata
>> in a way that a client application is likely to recognise
>> them as nodata.
>> By default pixels which are assigned no value from the source
>> dataset are
>> set to zero.
>
>
> I am not sure if I could tell clearly what was my problem. I will try
> again. I have layers like this:
>
> LAYER
>          NAME "M138"
>          METADATA
>            "wcs_label"    "M138"
>            "OWS_EXTENT" "86000 6636000 650000 7518000"
> 	  "WCS_RESOLUTION" "0.5 0.5"
> 	  "WCS_SIZE" "50000 50000"
> 	  "WCS_BANDCOUNT" "1"
>          END
>          STATUS ON
>          TILEINDEX "d:/dataM138"
>          TYPE RASTER
>          UNITS METERS
>          SIZEUNITS PIXELS
>          OFFSITE 0 0 0
>          TOLERANCE 3
>          TOLERANCEUNITS PIXELS
>          PROJECTION
>            "init=epsg:3067"
>          END
>          DUMP TRUE
>    END
>
> Tiles combined by M138_WMS.shp overlap because they are reprojected.
> When I use this layer through WMS, having OFFSITE 0 0 0 makes the black
> nodata triagles transparent and warped images make a seamless mosaic.
> Somehow I was awaiting that WCS behaves in a similar way, but it does
> not. Black nodata triangles are burned into the output image and the
> mosaic is useless. I can get my job done by hand editing WMS calls so
> that the BBOX and WIDTH and HEIGHT give me the desired pixel size, but
> it would be a bit more simple through WCS GetCoverage and ResX, ResY.
>
> -Jukka-
> _______________________________________________
> mapserver-users mailing list
> mapserver-users at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/mapserver-users
>