[gdal-dev] gdalwarp makes landcover files blocky when shrinking pixel size

John Twilley mathuin at gmail.com
Fri Jan 27 13:00:55 EST 2012

I've never seen gdaladdo -- neat command!  Alas, the overviews are the
wrong way 'round -- I don't need to zoom out, I need to zoom in.
gdaladdo doesn't handle fractional scale values well, so I can't make
something bigger out of something smaller like I can with gdalwarp.

mathuin at gmail dot com

On Thu, Jan 26, 2012 at 20:01, Chaitanya kumar CH
<chaitanya.ch at gmail.com> wrote:
> John,
> Try gdaladdo [1] with the resampling algo set to 'mode'. If you use the -ro
> option, it will create an external overview. Check your output with
> different combinations of levels.
> [1]: http://www.gdal.org/gdaladdo.html
> On Fri, Jan 27, 2012 at 5:09 AM, John Twilley <mathuin at gmail.com> wrote:
>> I am working with elevation and landcover data downloaded from the
>> USGS.  I use gdalwarp to convert the data to a much smaller pixel. The
>> elevation data works very nicely with cubic resampling, but the only
>> resampling that works at all for the landcover data is
>> nearest-neighbor and that's very blocky.  When I last worked with
>> landcover data, I used a majority algorithm which produced smoother
>> output -- but that algorithm is not implemented in gdalwarp.
>> I am looking over the source to gdalwarp to see how hard it is to add
>> a new algorithm.  Other than that, though, what options are available
>> to me?  Thanks in advance!
>> Jack.--
>> mathuin at gmail dot com
>> _______________________________________________
>> gdal-dev mailing list
>> gdal-dev at lists.osgeo.org
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> --
> Best regards,
> Chaitanya kumar CH.
> +91-9494447584
> 17.2416N 80.1426E

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