[gdal-dev] I have a problem getting higher resolution in a VRT file

[Stephen Woodbridge]

Jukka,

Thanks those are great threads and very educational.
I solved my problem. I was using upsample="bilinear" rather than 
upsampling="bilinear" and fixing this gave the expected results. But if 
not for my stupid typo, I would not have had a chance to read those 
threads and google others regarding upsampling.

Thanks for the assist,
-Steve

On 8/20/2020 10:13 AM, Rahkonen Jukka (MML) wrote:
> Hi,
>
> Resampling is science that would be nice to understand. Unfortunately I don't but I think that this thread is worth reading osgeo-org.1560.x6.nabble.com/gdal-dev-downsampling-geotiff-with-a-low-pass-filter-td5385890.html. In this gis.SE question cubic spline was considered good https://gis.stackexchange.com/questions/30627/smoothing-reinterpolating-raster-with-gdal.
>
> -Jukka-
>
> -----Alkuperäinen viesti-----
> Lähettäjä: Stephen Woodbridge <stephenwoodbridge37 at gmail.com>
> Lähetetty: torstai 20. elokuuta 2020 16.58
> Vastaanottaja: Rahkonen Jukka (MML) <jukka.rahkonen at maanmittauslaitos.fi>
> Aihe: Re: [gdal-dev] I have a problem getting higher resolution in a VRT file
>
> Hi Jukka,
>
> Any thoughts on what would be a better way to upsample and image using GDAL?
>
> I assumed, maybe incorrectly, that if I’m up sampling between two pixels with values of say 1 and 2 that a new pixel 50% between them would get a value of 1.5 and at 25% would get a value 1.25 etc. using linear interpolation and bilinear would also account for rows above and below the current row.
>
> Even, I specified resampling=“bilinear” in the vrt file is this ignored?
>
> Thanks, Steve
>
> Sent from my iPhone
>
>> On Aug 20, 2020, at 8:23 AM, jratike80 <jukka.rahkonen at maanmittauslaitos.fi> wrote:
>>
>> Even Rouault-2 wrote
>>> ...
>>> By default, VRT uses nearest resampling. You must specify something else.
>>> Look for "A resampling attribute can be specified" in
>>> https://gdal.org/drivers/raster/vrt.html
>>> ...
>>>
>>> --
>> Actually in the provided .vrt file I can see <SimpleSource
>> resample="bilinear">
>>
>> But isn't bilinear unsuitable for upsampling and some more blurring
>> method might work better?
>>
>> -Jukka Rahkonen-
>>
>>
>>
>> --
>> Sent from: http://osgeo-org.1560.x6.nabble.com/GDAL-Dev-f3742093.html
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