[gdal-dev] WCS GetCoverage with AxisOrder swap

[Peter Baumann]

On 11/08/2017 10:01 PM, Ari Jolma wrote:
>
> Even Rouault kirjoitti 08.11.2017 klo 17:31:
>
>> On mercredi 8 novembre 2017 15:50:48 CET Piero Campalani wrote:
>>
>>
>> > This order is what can be referred to in the GridFunction: +1 --> first
>>
>> > GRID axis, +2 --> second GRID axis, etc.
>>
>
> Ok, this tells me that the axisOrder attribute in sequenceRule determines how
> to consider the GridEnvelope and the order of the offsetVectors in the Grid
> element.

the axisLabels attribute determines axis order, and this in turn refers to the
CRS definition behind the URL in srsName.
SequenceRule / GridFunction is just for the internal linearization (whose
description depends, ie: interprets axis order) - and BTW only applies to GML
(and JSON and RDF), not necessarily to binary encodings which usually determine
their own internal structure.

My team has analysed your report and says:

On 11/08/2017 02:56 PM, Bang Pham Huu wrote:
>
> I checked the result as I think it is like this
>
> + GeoServer is correct with http://www.opengis.net/def/crs/EPSG/0/2393 as this
> one is X, Y so the offset vector is correct.
>
> offsetVector1: X (positive), Y (negative)
>
> offsetVector2: Y (negative), X (positive)
>
> + Rasdaman is also correct with http://ows.rasdaman.org/def/crs/EPSG/0/4326
> (Lat, Long) so the offset vector is correct.
>
> offsetVector1: Y (negative), X (positive)
>
> offsetVector2: X (positive), Y (negative)
>
> and with a CRS with X, Y order like
> http://www.opengis.net/def/crs/EPSG/0/3857, Rasdaman returns offset vector
> with correct order, e.g from a 2D coverage imported with this CRS:
>
> <offsetVectorsrsName="http://localhost:8080/def/crs/EPSG/0/3857">23613.2868316
> 0</offsetVector>
> <offsetVectorsrsName="http://localhost:8080/def/crs/EPSG/0/3857">0
> -23613.2868316</offsetVector>
>
> + Mapserver is not correct for http://www.opengis.net/def/crs/EPSG/0/4326 (it
> should be as same as Rasdaman).
>
>


-Peter

>
>>
>>  And thus MapServer output at
>>
>> http://194.66.252.155/cgi-bin/BGS_EMODnet_bathymetry/ows?SERVICE=WCS&REQUEST=DescribeCoverage&version=2.0.1&coverageid=BGS_EMODNET_CentralMed-MCol
>>
>> could probably be correct, but it would be better for
>> RectifiedGrid.axisLabels to be changed to "long lat" to better
>>
>> reflect what is done.
>>
>
> At least it fixes the driver for MapServer in this case (no hack options
> needed) since it does not define the axisOrder.
>
>> And GeoServer output at
>> https://msp.smartsea.fmi.fi/geoserver/wcs?SERVICE=WCS&REQUEST=DescribeCoverage&VERSION=2.0.1&COVERAGEID=smartsea__eusm2016-EPSG2393
>>
>> would either need to remove the GridFunction (ala MapServer) or keep it and
>> invert the order in which its offsetVector appear (ala Rasdaman)
>>
>
> Invert the offsetVector order *and* invert the axis in GridEnvelope (otherwise
> the size is wrong).
>
>>  
>>
>>  
>>
>> And for WCS subsetting, when you write something like SUBSET=AXIS_NAME(min,max),
>>
>> where AXIS_NAME should come from ? From the RectifiedGrid.axisLabels I guess ?
>>
>> (to be opposed to CoverageDescription.boundedBy.Envelope at axisLabels)
>>
>> Then in Ari's test with GeoServer
>>
>> https://msp.smartsea.fmi.fi/geoserver/wcs?SERVICE=WCS&REQUEST=DescribeCoverage&VERSION=2.0.1&COVERAGEID=smartsea__eusm2016-EPSG2393,
>> in theory "i" and "j" should be the axis requested ?
>>
>
> That does not work -- it's good that they are different since that shows it is
> not ok (invalid axis label error). Maybe the logic is related to the axis
> names? It's hard to tell since I don't find the logic in the GeoServer source
> code.
>
> Ari
>
>
>
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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)
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