[gdal-dev] WCS driver work

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[gdal-dev] WCS driver work

Ari Jolma-2
I've got very close to being able to get valid data (visual comparison
in QGIS) from various server types and WCS versions.

I've documented the results here:
https://trac.osgeo.org/gdal/wiki/WCS%2Binteroperability

It seems that I need eight option flags to cover all cases. Mostly the
problems are with CRS that have inverted axis order. Also it seems to be
a problem if the server or the standard does not support requesting
directly tiles of specific size. It is especially a problem since GDAL
fails the call if the size is not expected.

The only combination that I have not yet managed to get to work is
GeoServer with version 1.1 and inverted axis order. I can get a decent
response but the returned geotiff has slightly wrong size (59x38 instead
of 60x38). The problematic call is below[1].

Also, I have/know only a few servers and I lack some combinations; I've
also found a server with a combination that I've managed to test ok, but
whose behavior I can't yet explain[2].

I'm writing documentation and test code but the latter will still take
some time to be ready for the trunk.

The code is at https://github.com/ajolma/gdal/tree/trunk/gdal/frmts/wcs

I've also made one ticket regarding port code
https://trac.osgeo.org/gdal/ticket/7141

Ari

[1]
https://msp.smartsea.fmi.fi/geoserver/wcs?SERVICE=WCS&VERSION=1.1.0&REQUEST=GetCoverage&IDENTIFIER=smartsea%3Aeusm2016-EPSG2393&FORMAT=image%2Ftiff&BOUNDINGBOX=6620001.14539506,3199988.18514013,6670001.21326246,3279980.29051582,urn:ogc:def:crs:EPSG::2393&RangeSubset=contents&GridBaseCRS=urn:ogc:def:crs:EPSG::2393&GridCS=urn:ogc:def:cs:OGC:0.0:Grid2dSquareCS&GridType=urn:ogc:def:method:WCS:1.1:2dGridIn2dCrs&GridOrigin=6670001.21326246,3199988.18514013&GridOffsets=0,1333.20175626157,-1315.79125966838,0

[2]
https://lists.osgeo.org/pipermail/mapserver-users/2017-November/080339.html


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Re: WCS driver work

Ari Jolma-2
Ari Jolma kirjoitti 14.11.2017 klo 17:41:

> I've got very close to being able to get valid data (visual comparison
> in QGIS) from various server types and WCS versions.
>
> I've documented the results here:
> https://trac.osgeo.org/gdal/wiki/WCS%2Binteroperability
>
> It seems that I need eight option flags to cover all cases. Mostly the
> problems are with CRS that have inverted axis order. Also it seems to
> be a problem if the server or the standard does not support requesting
> directly tiles of specific size. It is especially a problem since GDAL
> fails the call if the size is not expected.
>
> The only combination that I have not yet managed to get to work is
> GeoServer with version 1.1 and inverted axis order. I can get a decent
> response but the returned geotiff has slightly wrong size (59x38
> instead of 60x38). The problematic call is below[1].

I was able to fix this by computing the pixel size a bit differently
(kind of numeric problem again, since you want n pixels, the pixel size
needs to be computed like you need n+0.5 pixels).

Ari

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