[GRASS-user] [GRASS]Problem importing geotiff with r.in.gdal

[Frank Warmerdam]

Raffaello Brondi wrote:
> hi all
> 
> I'm developing a processing-service using GRASS and I've got a problem 
> when importing GeoTiff rasters.
> 
> The import operation is implemented by means of r.in.gdal
> 
> When I import a geotiff created by means of a WCS request using 
> geoserver 1.5, the data is shifted by half a pixel; that is, the point 
> of origin has half a pixel offset.
> 
> The problem seems to be due to a wrong handling of meta-tags by r.in.gdal.
> 
> The import works correctly (without any shift) if geotiffs with the 
> meta-tag AREA_OR_POINT=Area are imported. However, a WCS request to 
> geoserver 1.5 results in a geotiff using AREA_OR_POINT=point. It seems 
> that Grass ignores the difference: the coordinates of the point of 
> origin are handled as if they refer to the corner, instead of the center 
> of the pixel.
> 
> I've looked at gdal options, but I found nothing about this. Has anyone 
> encontered the same problem?

Raffaello,

This is a long standing issue with GDAL and geotiff.  I take the position
that pixel-is-point in geotiff does not change the interpretation that should
be made of the tie point while some others take the opposite opinion.

I don't have any suggestions for how to work around this.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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