[gdal-dev] GML lat-lon coverages and interoperability

Mon Apr 3 23:55:55 PDT 2017

Hi,

Adding mapserver-dev to recipients in hope that Stephan Meissl notices and could share his opinion.  Mapserver WCS 2.0.1 does not generate axisOrder.

-Jukka Rahkonen-

________________________________
Lähettäjä: Even Rouault <even.rouault at spatialys.com>
Lähetetty: 3. huhtikuuta 2017 23:03
Vastaanottaja: gdal-dev at lists.osgeo.org
Kopio: Rahkonen Jukka (MML); Andrea Aime; geoserver-devel at lists.sourceforge.net
Aihe: Re: [gdal-dev] GML lat-lon coverages and interoperability

On lundi 3 avril 2017 13:19:18 CEST Rahkonen Jukka (MML) wrote:

> Great, first hit from Andrea. I am awaiting if Even strikes back.

I don't really have an opinion on this. I haven't read the relevant part of the GML or GMLCOV spec and I'm afraid I wouldn't understand it well. The GDAL GMLJP2 code just follows what the GMLJP2 spec and examples suggest, as well as data productions. Perhaps it is not "correct"...

> His

> creation (GDAL JP2OpenJPEG driver) writes out EPSG:4326 coverage into GML

> JP2 this way, without having gridFunction.

> <gml:FeatureCollection

> xmlns:gml="http://www.opengis.net/gml"

> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

> xsi:schemaLocation="http://www.opengis.net/gml

> http://schemas.opengis.net/gml/3.1.1/profiles/gmlJP2Profile/1.0.0/gmlJP2Pro

> file.xsd">

<gml:boundedBy>

> <gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">

> <gml:lowerCorner>61.7282236395245 24.7248340978191</gml:lowerCorner>

> <gml:upperCorner>61.7838827490233 24.8422668729657</gml:upperCorner>

> </gml:Envelope>

> </gml:boundedBy>

> <gml:featureMember>

> <gml:FeatureCollection>

> <gml:featureMember>

> <gml:RectifiedGridCoverage dimension="2" gml:id="RGC0001">

> <gml:rectifiedGridDomain>

> <gml:RectifiedGrid dimension="2">

> <gml:limits>

> <gml:GridEnvelope>

> <gml:low>0 0</gml:low>

> <gml:high>15517 7354</gml:high>

> </gml:GridEnvelope>

> </gml:limits>

> <gml:axisName>x</gml:axisName>

> <gml:axisName>y</gml:axisName>

> <gml:origin>

> <gml:Point gml:id="P0001"

> srsName="urn:ogc:def:crs:EPSG::4326">

<gml:pos>61.7838789652633

> 24.7248378815791</gml:pos> </gml:Point>

> </gml:origin>

> <gml:offsetVector srsName="urn:ogc:def:crs:EPSG::4326">0

> 7.56751998624388e-006</gml:offsetVector>

<gml:offsetVector

> srsName="urn:ogc:def:crs:EPSG::4326">-7.56751998624388e-006

> 0</gml:offsetVector> </gml:RectifiedGrid>

> </gml:rectifiedGridDomain>

> <gml:rangeSet>

> <gml:File>

> <gml:rangeParameters/>

> <gml:fileName>gmljp2://codestream/0</gml:fileName>

> <gml:fileStructure>Record Interleaved</gml:fileStructure>

> </gml:File>

> </gml:rangeSet>

> </gml:RectifiedGridCoverage>

> </gml:featureMember>

> </gml:FeatureCollection>

> </gml:featureMember>

> </gml:FeatureCollection>

>

> -Jukka-

>

> Lähettäjä: andrea.aime at gmail.com [mailto:andrea.aime at gmail.com] Puolesta

> Andrea Aime

Lähetetty: 3. huhtikuuta 2017 15:58

> Vastaanottaja: Rahkonen Jukka (MML) <jukka.rahkonen at maanmittauslaitos.fi>

> Kopio: 'gdal-dev at lists.osgeo.org' (gdal-dev at lists.osgeo.org)

> <gdal-dev at lists.osgeo.org>; geoserver-devel at lists.sourceforge.net

Aihe:

> Re: [gdal-dev] GML lat-lon coverages and interoperability

>

> On Mon, Apr 3, 2017 at 2:32 PM, Rahkonen Jukka (MML)

> <jukka.rahkonen at maanmittauslaitos.fi<mailto:jukka.rahkonen at maanmittauslaito

> s.fi>> wrote:

With orthophoto coverages I believe that all cases could be

> handled with the default gridFunctions: startPoint at gml:Low, axisOrder +1

> +2, sequence rule “Linear”. As far as I have understood GDAL trusts that

> this is also what the other partners do. However, it seems that GeoServer

> developers have decided to handle the latitude-longitude axis flip in WCS

> 2.0.1 by changing the order of grid axis with a function instead of writing

> the offsetVectors to suit with the default +1 +2 axis order.

> <gml:coverageFunction>

> <gml:GridFunction>

> <gml:sequenceRule axisOrder="+2 +1">Linear</gml:sequenceRule>

> <gml:startPoint>0 0</gml:startPoint>

> </gml:GridFunction>

> </gml:coverageFunction>

>

> Hi Jukka,

> the decision was not arbitrary, and imho, necessary.

>

> Rasters pixels are normally represented as east/north, but OGC forces us to

> describe geographic data in lat/lon order.

So how do you tell the client,

> "look, I'm telling you that the axis order is north/east, but really, I'm

> giving you back data in east/north order instead"?

> Cheers

> Andrea

>

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