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

[John Twilley]

Cubic is fine for the elevation, but it doesn't work on the landcover.
which is the problem I originally mentioned.

Jack.
--
mathuin at gmail dot com



2012/1/27 Dmitry Baryshnikov <polimax at mail.ru>:
> 27.01.2012 20:19, John Twilley пишет:
>
>> After retrieving the files and building VRTs from them, I run the
>> following gdalwarp commands:
>>
>> gdalwarp -q -multi -t_srs "+proj=aea +datum=NAD83 +lat_1=29.5
>> +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +units=m" -tr 6 6 -te
>> 2002944 2271744 2016768 2288640 \
>>  -srcnodata -340282346638528859811704183484516925440 -dstnodata 0
>> ND302HT.vrt ND302HT.tif
>> gdalwarp -q -multi -t_srs "+proj=aea +datum=NAD83 +lat_1=29.5
>> +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +units=m" -tr 6 6 -te
>> 2002944 2271744 2016768 2288640 \
>>  -srcnodata 255 -dstnodata 11 L0102HT.vrt L0102HT.tif
>>
>> The only differences between the lines are the nodata values.
>>
>> Jack.
>> --
>> mathuin at gmail dot com
>>
>>
>>
>> On Thu, Jan 26, 2012 at 22:49, Dmitry Baryshnikov<polimax at mail.ru>  wrote:
>>>
>>> 27.01.2012 3:39, John Twilley пишет:
>>>>
>>>> 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
>>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>>>>
>>>>
>>> Hi John,
>>>
>>> That is your command line string for gdalwarp?
>>>
>>> Best regards,
>>> Dmitry
>>>
>>> _______________________________________________
>>> gdal-dev mailing list
>>> gdal-dev at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>
> Hi John,
>
> Try to add "-r cubic" command parameter
> For example:
>
>
> gdalwarp -q -multi -t_srs "+proj=aea +datum=NAD83 +lat_1=29.5
> +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +units=m" -tr 6 6 -r cubic
> -te
>
> 2002944 2271744 2016768 2288640 \
>  -srcnodata -340282346638528859811704183484516925440 -dstnodata 0
> ND302HT.vrt ND302HT.tif
>
> You can found additional parameters description here:
> http://www.gdal.org/gdalwarp.html
> I have tested -r parameter and it works.
>
>
> Best regards,
> Dmitry
>
>
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