[GRASS-user] GRASS export GeoTiff adventure :-)

Maciej Sieczka tutey at o2.pl
Mon Aug 11 23:20:59 EDT 2008

Markus Metz pisze:
> Nikos Alexandris wrote:

>> 7. Exporting a group (the ones that automatically are created for
>> each imported photo and contain the red, green and blue components 
>> respectively), gives "INTERLEAVE=PIXEL" but "Block=2500x3". Is it 
>> correct to force createopt="BLOCKYSIZE=1" which gives
>> "Block=2500x1"?

> BLOCKXSIZE and BLOCKYSIZE affect the tile size, as far as I
> understand the gdal documentation. I would not change the defaults.
> Leaving BLOCKXSIZE on default = 256 and setting BLOCKYSIZE to 1
> should produce tiles of size 256x1.

The explanation on GDAL ML:


I prefer to enforce "BLOCKYSIZE=1" because this assures best rendering
prformance in QGIS for me.

>> 8. There are several compression methods? Does compression affect 
>> significantly reading/displaying an image?

> I would stay away from tiff internal compression because other
> software might not support it (LZW and DEFLATE are sometimes not
> supported).

 From my limited experience with ESRI products, LZW dose not pose
problems and provides an optimal tradeoff between the render times and
file size. Deflate seems less supported and although compresses better
requires more CPU power to decompress.

> TFW=YES would only be needed if you export a raster for an
> application that can not read GeoTIFF internal metadata.

Yet it never hurts to create a TFW just in case ;).


Maciej Sieczka

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