[Qgis-user] (no subject)

[Alex Mandel]

What tool in QGIS are you using to adjust the raster? Can you please
include the exact command you are currently using.

If you are using something from the Raster Menu (aka GDAL Tools) then
you need to set the compression and type of number manually.

The type of number stored dictates a large amount of overhead, there is
a huge difference between Integer and Float.

-co COMPRESS=LZW  -ot Int16

See http://www.gdal.org/gdal_translate.html for options. Pick the
smallest type of number storage that holds your data correctly. Most
GDAL tools will default to Float, that is likely the difference.

Thanks,
Alex

On 07/26/2014 06:35 AM, Peter Versteeg wrote:
> Hello,
> 
> I use arcmap desktop 10.2.2. In the workflow i use atm i make a geotiff
> using the export map option in arcmap.
> 
> I need 4000dpi and i use geotiff tags and compression (LZW).
> 
> The resolutions of my geotiff is.
> 
> See png
> 
> [image: rasterinfo.png]
> <https://geonet.esri.com/servlet/JiveServlet/showImage/2-391241-2616/rasterinfo.png>
> 
> I use the geotiff as raster for a 3D simulation. The software i use for
> this needs a specific resolution.
> 
> They need to by in the power of 2.  So the rows and columns need to by
> 4096, 8192, 16384, 32768, 65536, 131072 etc.
> 
> I use QGIS to adjust the resolution. see png
> 
> [image: rasterqgis.png]
> <https://geonet.esri.com/servlet/JiveServlet/showImage/2-391241-2617/rasterqgis.png>
> 
> 
> 
> What i found out is that QGIS is not good with compression. My arcmap
> export fire is 120k. The file QGIS makes is 6292k without compression and
> 4194 with compression.
> 
> 
> 
> Also the low and high compression file size is the same and JPEG is not
> working.
> 
> 
> 
> Why is the file size so big and what can i do about it.
> 
> 
> 
> thank you and greetings Peter
> 
> 
> 
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