[gdal-dev] wcs extraction

[Bruno Binet]

Thanks you very much Frank for the clarification.
You confirm what I understood.

Best regards,
Bruno

On 11 February 2010 16:54, Frank Warmerdam <warmerdam at pobox.com> wrote:
> Bruno Binet wrote:
>>
>> Hi list,
>>
>> I'm currently trying to use the wcs gdal driver to extract data from a
>> wcs service (mapserver), using a specfic projection, extent and
>> resolution.
>> I managed to extract the all dataset in the original projection, and
>> format (geotiff).
>> But I would like to be able to specify a value for the format, the
>> extent, the projection, and the resolution for the data to be
>> extracted.
>>
>> Given the docs: http://www.gdal.org/frmt_wcs.html we can specify a
>> preferred format for extraction with the PreferredFormat element, but
>> what about projection, extent, and resolution?
>> Do we have to download the entire dataset and use gdal capabilities to
>> extract and reproject a subset of the downloaded data?
>> It would be great if it could be handled directly by mapserver.
>
> Bruno,
>
> I have skimmed the WCS driver implementation and it does not appear
> to be convenient to request data in a projection other than the default.
> Basically the driver really wants to establish an image size and it does
> this from the GridCRS/BoundingBox (1.1) or GridEnvelope (1.0) and this
> information is generally (always?) only available for the default coordinate
> system.
>
> It might be possible for you to manually massage all these values in
> the CoverageOffering/CoverageDescription in the GDAL WCS control file
> to "fake it out" as if another coordinate system was the default.  However,
> I've never tried that and it might be fairly hard to get right.
>
> As things are currently setup, it is really intended that GDAL "knows" the
> true native coordinate system, grid size and georeferencing and accesses
> on that basis.
>
> Best regards,
> --
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Programmer for Rent
>
>



-- 
Bruno Binet

Camptocamp France SAS
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Mail : bruno.binet at camptocamp.com
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