Fwd: [gdal-dev] Shift of geoTiff

[Paul Meems]

Forwarding Bens reply to the full list.
Ben is the user I mentioned in my start post.

Thanks,

Paul

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---------- Forwarded message ----------
From: Ben Jones <ben at malleefocus.com.au>
Date: 2010/6/8
Subject: RE: [gdal-dev] Shift of geoTiff
To: Frank Warmerdam <warmerdam at pobox.com>
Cc: bontepaarden at gmail.com


Hi Frank and Paul,
Thanks for following this up.
Note that it's a half pixel shift (not a full pixel).
I wasn't able to find a compiled version of listgeo so I can't check myself
- but will be interested to see what the output is.
As noted in the original post, the GeoTiff spec seems to call for pixels to
be referenced by their center and not their upper-left corner. If that's the
case, then according to the GDALINFO output, the outside pixel coordinates
should be the origin, and (cols - 1) x dx and (rows - 1) x dy away from the
origin. But they're cols x dx and rows x dy away from the origin in the
GDALINFO output. Which makes me think there's something going wrong in there
somewhere.
Cheers
Ben

-----Original Message-----
From: Frank Warmerdam [mailto:warmerdam at pobox.com]
Sent: Tuesday, 8 June 2010 12:51 AM
To: Paul Meems
Cc: gdal-dev at lists.osgeo.org; Ben Jones
Subject: Re: [gdal-dev] Shift of geoTiff

Paul Meems wrote:
> One of our user of MapWindow GIS noticed a shift of its geotiff by one
> pixel width.
>
> I took a look at it to see if the problem is with MapWindow or GDAL,
> because MapWindow uses GDAL internally.
>
> The provided metadata of the geotiff is:
> GROUP = L1_METADATA_FILE
>   GROUP = METADATA_FILE_INFO
>     ORIGIN = "Image courtesy of the U.S. Geological Survey"

Paul,

I imagine GDAL is getting it's georeferencing from the GeoTIFF itself
rather than from the supporting metadata file.  What does the listgeo
report on the geotiff file look like?

Best regards,
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