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

[Rahkonen Jukka (MML)]

Great, first hit from Andrea. I am awaiting if Even strikes back. 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/gmlJP2Profile.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 maanmittauslaitos.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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