[gdal-dev] WCS driver

[Peter Baumann]

FYI, this is one of the shortcomings of WCS 1.x. Remedied in WCS 2.

-Peter


On 10/28/2017 04:39 PM, Ari Jolma wrote:
> jratike80 kirjoitti 28.10.2017 klo 13:10:
>
>> Ari Jolma-2 wrote
>>>
>>> For example this request to a MapServer WCS (I'm not responsible for
>>> that server so don't know much about it), which is generated in the
>>> driver during a DescribeCoverage for the coverage,
>>>
>>> http://194.66.252.155/cgi-bin/BGS_EMODnet_bathymetry/ows?SERVICE=WCS&VERSION=1.1.1&REQUEST=GetCoverage&IDENTIFIER=BGS_EMODNET_CentralMed-MCol&FORMAT=image%2Ftiff&BOUNDINGBOX=9.833333335,46.183333325,9.837500005,46.187499995,urn:ogc:def:crs:EPSG::4326&RangeSubset=band
>>>
>>>
>>> gets the response
>>>
>>> WCS server error. Requested BBOX
>>> (46.183333325,9.833333335,46.187499995,9.837500005) is outside requested
>>> coverage BBOX (9.83125,30.01040372,22.23542659,46.18958333)
>>>
>>> If I change the order of X and Y in the bounding box in the request, the
>>> reply is ok.
>> Hi,
>>
>> BoundingBoxes in WCS 1.1.x and 2.x must follow the axis order of the
>> coordinate system, so with urn:ogc:def:crs:EPSG::4326 it must be
>> latitude-longitude.
>
> ok, this is the famous confusion concerning axis order.
>
> To me it seems that GDAL is correct since it determines the bounding box
> originally from GridCRS in CoverageDescription where the origin is said to be
> "9.833333335 46.187499995" (i.e., lon-lat). In the same GridCRS the CRS is
> stated to be "urn:ogc:def:crs:EPSG::4326" - so the axis order could be assumed
> correct. Interestingly in the same CoverageDescription MapServer says the
> LowerCorner of the "urn:ogc:def:crs:EPSG::4326" BoundingBox is "30.01040372
> 9.83125" (i.e., lat-lon). So it seems to me that MapServer is contradicting
> itself.
>
> Reading MapServer code, it seems to be based on the idea that x,y is always
> east,north and when it writes BoundingBox, it swaps x and y if the projection
> is inverted (like 4326). It does not do that when it writes GridCRS.
>
> GDAL seems to be based on the idea that x,y is what the projection says (what
> the projection says could be found out with OGRSpatialReference::GetAxis -
> however, for 4326 it does not say anything). This is my impression from WCS
> driver - I see there's a lot on this issue in the GML driver page.
>
> A fix could be a WCS driver option "swap axis order for bounding box". But
> since I think that is not fixing the root cause (lying twice does not make you
> a truth speaker), also an option "swap axis order when reading GridOrigin" is
> needed. Isn't this fun?
>
>
>>   EPSG:3067 is natively an easting-northing system and
>> therefore it can make you believe that everything works fine but if you test
>> the Finnish services also with northing-easting system EPSG:2393 you may get
>> more frustration.
> I'm sure you mean 'fun'.
>>
>> An open Geoserver with a DEM of Finland is available for testing at
>> http://avoindata.maanmittauslaitos.fi/geoserver/wcs?service=WCS&version=2.0.1&request=GetCapabilities
>>
>
> I'll try the axis order with that. The geoserver at msp.smartsea.fmi.fi is
> mine and I'm not sure how well I can manage a geoserver.
>
> Ari
>
>>
>> -Jukka Rahkonen-
>>
>>
>>
>>
>> -- 
>> Sent from: http://osgeo-org.1560.x6.nabble.com/GDAL-Dev-f3742093.html
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-- 
Dr. Peter Baumann
 - Professor of Computer Science, Jacobs University Bremen
   www.faculty.jacobs-university.de/pbaumann
   mail: p.baumann at jacobs-university.de
   tel: +49-421-200-3178, fax: +49-421-200-493178
 - Executive Director, rasdaman GmbH Bremen (HRB 26793)
   www.rasdaman.com, mail: baumann at rasdaman.com
   tel: 0800-rasdaman, fax: 0800-rasdafax, mobile: +49-173-5837882
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