[gdal-dev] help resampling raster to coarser scale

[Chaitanya kumar CH]

Etienne,

You can find a lot of sample code in the gdal test scripts[1]. There is a
test script for regenerating overviews in gcore/tiff_ovr.py [2].

You can apply a filter using a VRT file[3]. It supports filters of various
sizes.

[1]: http://trac.osgeo.org/gdal/browser/trunk/autotest/
[2]:
http://trac.osgeo.org/gdal/browser/trunk/autotest/gcore/tiff_ovr.py#L1046
[3]: http://www.gdal.org/gdal_vrttut.html

On Sat, Aug 6, 2011 at 5:15 AM, Etienne <etiennesky at yahoo.com> wrote:

> Thanks Anton
>
> This might seem obvious to many of you, but how could I go about applying a
> filter using the gdal utilities/functions/python code?
>
> Etienne
>
>
> ----- Original Message -----
> From: Anton Korosov <anton.korosov at nersc.no>
> To: gdal-dev at lists.osgeo.org
> Cc:
> Sent: Friday, August 5, 2011 3:27:41 AM
> Subject: Re: [gdal-dev] help resampling raster to coarser scale
>
> Hi Etienne!
>
> What if you first process the original fine resolution image with a
> filter (low-pass, median, or manually created pixel function). Then the
> result, which is a fine resolution image but smoothed, could be
> resampled with the nearest neighbor.
>
> Anton
>
> On 08/05/2011 03:57 AM, Etienne wrote:
> > Hi all,
> >
> >
> > I am trying to resample a raster with categorical data (land surface
> vegetation/cover) from a high resolution (500m) to a coarser resolution.
> >
> > I would like to do something similar to what the GRASS operator
> r.resamp.stats does, using the modal category present in the higher
> resolution dataset to pick the value in the lower-resolution map.
> > It seems that my only option using gdal_warp is nearest neighbor, which
> will pick the value nearest to the coarser pixel center (regardless of the
> most present category within the region).
> >
> > I would also like have a low-resolution map with the proportions of all
> land types (from the high resolution map).
> >
> > Any idea on how to accomplish what I want using gdal?  I am not familiar
> with GRASS, and would prefer to stick with GDAL if I can.  However, I am
> open to any suggestions.
> >
> > Many Thanks
> > Etienne
> > _______________________________________________
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> > gdal-dev at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/gdal-dev
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-- 
Best regards,
Chaitanya kumar CH.

+91-9494447584
17.2416N 80.1426E
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