[gdal-dev] WCS GetCoverage with AxisOrder swap

[Even Rouault]

Peter,

> the axisLabels attribute determines axis order, and this in turn refers to the
> CRS definition behind the URL in srsName.

Does the value of RectifiedGrid.axisLabels must be correlated with the one of the CRS,
or can it be a "random" value ?
For example, GeoServer has <gml:RectifiedGrid><gml:axisLabels>i j</gml:axisLabels></gml:RectifiedGrid>

> My team has analysed your report and says:

Thanks but I'm afraid I'm even more confused now.

> 
> 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.

In EPSG, http://www.opengis.net/def/axis/EPSG/0/48 = X = NORTH and 
http://www.opengis.net/def/axis/EPSG/0/47 = Y = EAST. So this CRS has the "GIS-unfriendly" order.

But if you consider
<gml:Envelope srsName="http://www.opengis.net/def/crs/EPSG/0/2393" axisLabels="Y X" uomLabels="m m" srsDimension="2">
<gml:lowerCorner>6543350.381089335 3061592.6391462097</gml:lowerCorner>
<gml:upperCorner>7307056.899896299 3432141.361396798</gml:upperCorner></gml:Envelope>

and assume from the above that Y=EAST=6543350.381089335 and X=NORTH=3061592.6391462097 (lower corner values),
this doesn't transform to a location in Finland.

Whereas X=NORTH=6543350.381089335 and Y=EAST=3061592.6391462097 does transform to Finland

So I think the axisLabels here is wrong, it should be axisLabels="X Y"


> > 
> > offsetVector1: X (positive), Y (negative)
> > 
> > offsetVector2: Y (negative), X (positive)

Can't correlate the above reasoning about the sign of values with the actual output of
https://msp.smartsea.fmi.fi/geoserver/wcs?SERVICE=WCS&REQUEST=DescribeCoverage&VERSION=2.0.1&COVERAGEID=smartsea__eusm2016-EPSG2393
which is
<gml:offsetVector srsName="http://www.opengis.net/def/crs/EPSG/0/2393">0.0 20.00803035910304</gml:offsetVector>
<gml:offsetVector srsName="http://www.opengis.net/def/crs/EPSG/0/2393">-20.00803035910304 0.0</gml:offsetVector>

Given what you said about <gml:GridFunction> not applying to GeoTIFF output, then
this would be correct since the above would express that the first axis (along the width of the image) of the GeoTIFF
express positive easting space and the second axis (along height) express negative northing spacing (image north-up oriented)

Even

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