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

[Rahkonen Jukka (MML)]

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
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/gdal-dev