[Gdal-dev] r.out.gdal vs gdal_translate vs gdalwarp

[Maciej Sieczka]

Frank Warmerdam wrote:
> Maciej Sieczka wrote:
>> 'Frank Warmerdam-2' wrote:

>> Frank,
>> 
>> Thanks much for your answer! I'm so glad the hear this is not a
>> data corruption issue or whatsoever. However, wouldn't you
>> consider it a missfeature that gdalwarp creates circa 25% bigger
>> GeoTIFFs than gdal_translate does? The bigger deal it is the 
>> bigger is the input dataset.  For me it is quite a difference
>> whether I get a 3 GB or 4 GB raster. Do you think gdalwarp could
>> follow gdal_translate in this regard? If possible of course.

> The particular problem I saw in the case I analysed should actually
> get less and less significant as the dataset gets larger.  If you
> are seeing much larger files for big files then a different issue is
> likely to be coming into play.

Sorry for long time no reply. I have had an opportynity to dig into
this in some more detail at last. Indeed the bigger (in general) the
output dataset, the smaller the difference in gdal_translate and
gdalwarp output size. At circa 230 kB, the difference becomes almost
neglectable.

More info on the graph [1] (X axis should read "gdal_translate output
size [kB]" - sorry for this glitch).

Each raster was created and "measured" by script [2] and those
measurements were used to create the graph. The very input raster is
here [3].

One conclussion is that if someone creates, say, 500 10 kB rasters with
gdal_translate, they occupy 5 MB, while if created with gdalwarp it's 2
times more. This is a drastic scenario of course, but likely to happen.
Anyway, for anyone using GDAL to create rasters smaller than 200-250 kB
it is important. I'm one, and moreover I use those rasters as backdrop
on mobile GIS, where storage space is scarce.

I was wondering if, by any chance, it could be possible to make
gdalwarp to behave like gdal_translate in this respect?

Best Regards,
Maciek

[1]http://kufaya.googlepages.com/gt_vs_gw.pdf
[2]http://kufaya.googlepages.com/gt_vs_gw.txt
[3]http://kufaya.googlepages.com/one.tif