Why WCS 2.0.1 slice is not supported?

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Why WCS 2.0.1 slice is not supported?

jratike80

Hi,

 

Geoserver sends a one-pixel GeoTIFF with WCS request

 

demo.geo-solutions.it/geoserver/wcs?service=WCS&version=2.0.1&request=GetCoverage&coverageid=nurc__Img_Sample&subset=Long(-100)&subset=Lat(22)

 

Mapserver is sending an error message:

msWCSGetCoverage20(): WCS server error. Subset operation 'slice' is not supported.

 

Does Mapserver have some fundamental difficulties with finding the correct pixel and making GetCoverage response from it?

 

-Jukka Rahkonen-

 


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Re: Why WCS 2.0.1 slice is not supported?

Stephan Meißl
Hi Jukka,

in my opinion a one-pixel GeoTIFF is still a 2 dimensional coverage but
with two slice operations on a 2 dimensional coverage the result should
be 0 dimensional (each slice reduces the dimension by one).

In MapServer you could request using subsets with equal low and high,
e.g. &subset=Long(-100,-100)&subset=Lat(22,22), to retrieve a one-pixel
GeoTIFF.

cu
Stephan


On 11/20/2017 02:43 PM, Rahkonen Jukka (MML) wrote:

> Hi,
>
>  
>
> Geoserver sends a one-pixel GeoTIFF with WCS request
>
>  
>
> demo.geo-solutions.it/geoserver/wcs?service=WCS&version=2.0.1&request=GetCoverage&coverageid=nurc__Img_Sample&subset=Long(-100)&subset=Lat(22)
>
>  
>
> Mapserver is sending an error message:
>
> msWCSGetCoverage20(): WCS server error. Subset operation 'slice' is not
> supported.
>
>  
>
> Does Mapserver have some fundamental difficulties with finding the
> correct pixel and making GetCoverage response from it?
>
>  
>
> -Jukka Rahkonen-


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Re: Why WCS 2.0.1 slice is not supported?

jratike80
Hi Stephan,

Makes somewhat sense to the letter of the standard (though a layman may argue if there is difference between a number "1" and a range between "1" and "1"):
"A domain slice operation receives a dimension and a position (which must lie inside the coverage’s
domain) and delivers a coverage which is a slice of the offered coverage obtained at
the cutting position provided. The dimension of the result coverage is reduced by one as
compared to the original coverage."

 Also Rasdaman gives an error with
http://ows.rasdaman.org/rasdaman/ows?&SERVICE=WCS&VERSION=2.0.1&REQUEST=GetCoverage&COVERAGEID=BlueMarbleCov&SUBSET=Lat(0)&SUBSET=Long(0)&FORMAT=image/tiff
Error evaluating rasdaman query: 'SELECT encode(c[8999,4499], "tiff" , "{}") FROM BlueMarbleCov AS c'

Using GML or CSV as format does give a result
http://ows.rasdaman.org/rasdaman/ows?&SERVICE=WCS&VERSION=2.0.1&REQUEST=GetCoverage&COVERAGEID=BlueMarbleCov&SUBSET=Lat(0)&SUBSET=Long(0)&FORMAT=application/gml+xml

Should we say that Geoserver is doing it wrong? What if the data are of type "pixel is point"? Does Mapserver support an outputformat that supports slicing like GML or CSV in Rasdaman?

-Jukka Rahkonen-
________________________________________
Lähettäjä: mapserver-users <[hidden email]> käyttäjän  puolestaStephan Meißl <[hidden email]>
Lähetetty: 20. marraskuuta 2017 17:24
Vastaanottaja: [hidden email]
Aihe: [HUOM: VIESTIÄ EI VOITU VIRUSTARKASTAA SALAUKSEN TAKIA]  Re: [mapserver-users] Why WCS 2.0.1 slice is not supported?

Hi Jukka,

in my opinion a one-pixel GeoTIFF is still a 2 dimensional coverage but
with two slice operations on a 2 dimensional coverage the result should
be 0 dimensional (each slice reduces the dimension by one).

In MapServer you could request using subsets with equal low and high,
e.g. &subset=Long(-100,-100)&subset=Lat(22,22), to retrieve a one-pixel
GeoTIFF.

cu
Stephan


On 11/20/2017 02:43 PM, Rahkonen Jukka (MML) wrote:

> Hi,
>
>
>
> Geoserver sends a one-pixel GeoTIFF with WCS request
>
>
>
> demo.geo-solutions.it/geoserver/wcs?service=WCS&version=2.0.1&request=GetCoverage&coverageid=nurc__Img_Sample&subset=Long(-100)&subset=Lat(22)
>
>
>
> Mapserver is sending an error message:
>
> msWCSGetCoverage20(): WCS server error. Subset operation 'slice' is not
> supported.
>
>
>
> Does Mapserver have some fundamental difficulties with finding the
> correct pixel and making GetCoverage response from it?
>
>
>
> -Jukka Rahkonen-


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Re: Why WCS 2.0.1 slice is not supported?

Stephan Meißl
Hi Jukka,

> Makes somewhat sense to the letter of the standard (though a layman may argue if there is difference between a number "1" and a range between "1" and "1"):
True, but semantically it is different and we don't exclude a use case
if we don't allow one of both.

> Should we say that Geoserver is doing it wrong? What if the data are of type "pixel is point"? Does Mapserver support an outputformat that supports slicing like GML or CSV in Rasdaman?

Strictly speaking yes, but I assume they simply argue with a more
relaxed interpretation which is a valid approach I'd say. MapServer
could support such an outputformat but right now only 2d output is
supported.

cu
Stephan


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