[gdal-dev] HFA_USE_RRD vs USE_RRD

Mateusz Loskot mateusz at loskot.net
Fri Aug 1 19:04:01 EDT 2008

Maciej Sieczka wrote:
> Hi!
> If I use the followiwng syntax:
>  gdaladdo --config HFA_USE_RRD YES --config USE_RRD YES some.tif 2 4 8
> a small aux file and a big rrd file are created. If I use:
>  gdaladdo --config USE_RRD YES some.tif 2 4 8
> only a big aux is created.
> In the 1st case the sum of aux and rrd file sizes is equal the size of
> the aux file from the 2nd case.
> What is the difference between the 2 methods, is any better (in what
> terms) and could gdaladdo man page please address these issues
> (currently it only mentions USE_RRD alone).

The HFA_USE_RRD controls native overviews builder implemented 
specifically for a driver, HFA in this case.

The USE_RRD controls so called default overviews builder, for drivers 
that do not support it natively.

However, I'm unable to give in depth explanation what is the differences 
between these two types of overviews for HFA.

Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org

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