[gdal-dev] Erdas .img format (HFA) overview troubles

[Christiaan Janssen]

On the page http://www.gdal.org/frmt_hfa.html, it mentions the creation of .ovr files under the Creation Issue section. Also, am I wrong in thinking the command "gdaladdo -ro test.img 2 4 8" should have at least generated an .aux (or .rrd) file and not errored the way it did? Thanks.

Christiaan

-----Original Message-----
From: Frank Warmerdam [mailto:warmerdam at pobox.com] 
Sent: Monday, June 01, 2009 11:24 AM
To: Christiaan Janssen
Cc: gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] Erdas .img format (HFA) overview troubles

Christiaan Janssen wrote:
> After reading the HFA image format description, I was under the 
> impression that GDAL would support external .ovr files for this format 
> but it seems that is not the case. I ran quick test with gdaladdo 
> ("gdaladdo -ro test.img 2 4 8") and got the following error message:
> "ERROR 6: BuildOverviews() not supported for this dataset." After 
> poking through the code a bit I can see that HFA driver doesn't seem 
> to be using the default overview manager so it would seem that .ovr 
> files aren't actually ever being used (but i could be wrong). Was this 
> the intended result, or is this a bug?

Christiaan,

I believe this is the intended behavior.  HFA format overviews are always handling either in the .img file itself, in the .aux file or in an .rrd file.

If the documentation indicates otherwise, please point out the location and I'll attempt to clarify it.

Best regards,
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