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

[Chang Liao]

Has anyone looked into the so called regrid in Earth system model? How is
it different from GIS resampling?

Grid Remapping

ESMF has the option to build a standalone application, called *RegridWeightGen
<http://www.earthsystemcog.org/projects/regridweightgen>*, that can
generate interpolation weights in parallel. It's fast and can handle a wide
variety of grids and grid options. It's not necessary to use the rest of
ESMF to use it ... just provide grid files in a standard (netCDF-based)
format.

https://www.earthsystemcog.org/projects/esmf/

Thanks.



On Thu, Aug 20, 2020 at 8:40 AM Stephen Woodbridge <
stephenwoodbridge37 at gmail.com> wrote:

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

Best Regards!

Chang Liao,PhD
Earth Scientist, Atmospheric Sciences & Global Change Division
Pacific Northwest National Laboratory, WA, USA.
Email: changliao.climate at gmail.com  or  chang.liao at pnnl.gov
Personal Website: http://www.changliao.us
Skype: changliao1025
Lab Website: www.pnnl.gov
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