WCS: Origin of rectifiedGrid

[ajolma]

The origin of the rectifiedGrid is written (mapwcs.c:1193) as geotransform[0] and [3], which is extent boundaries. The origin should be expressed as the center of the grid point.

[rouault]

mapwcs.c is about WCS 1.0 and whole GDAL & MapServer code use pixel-corner convention, so I don't think things should be changed there
mapwcs11.c applies a half pixel shift for GridOrigin per https://github.com/mapserver/mapserver/blob/branch-7-0/mapwcs11.c#L724
So it looks the issue is for WCS 2.0 where this half pixel shift is not applied, but it should. @Schpidi any opinion ?

[ajolma]

Yes, sorry, I was too quick to point to the place in code. I saw the error in XML returned by a server when testing the new GDAL WCS driver in 2.0.1 mode.

[rouault]

Fix committed per 31c25df
Both GeoServer and Rasdaman also use the center of grid point convention, so this fix was needed.

[Schpidi]

@rouault I fully agree with the necessary changes, many thanks for taking care!

[ajolma]

I think this issue is also valid for 1.0.0. See for example http://194.66.252.155/cgi-bin/BGS_EMODnet_bathymetry/ows?SERVICE=WCS&REQUEST=DescribeCoverage&VERSION=1.0.0&COVERAGE=BGS_EMODNET_CentralMed-MCol
In 1.0.0 the origin is at the center of pixel in ArcGIS and GeoServer