[gdal-dev] EXT: Re: Rotated lat lon projection

Mon Sep 5 01:35:08 PDT 2022

Ok, thanks for the file. Here's a gist just to show you it works, I use R
so I've got some checks I do around the core gdalwarp call which can be as
minimal as

gdalwarp  20220902T00Z_MSC_HRDPS_HGT_SFC_RLatLon0.0225_P001.grib2 out.tif
-t_srs "OGC:CRS84"

You should consider the specification of the target grid yourself, with a
combination of some of -tr, -ts, -te, and -t_srs arguments. Also the -r
resampling argument, default is nearest neighbour.

https://gist.github.com/mdsumner/d73748c44aef4a0923760401d3dc605d

Cheers, Mike

On Mon, Sep 5, 2022 at 5:21 PM De Juan De España, Javier <
jajuan_ext at acciona.com> wrote:

> Hi Mike!
>
>
>
> Thank you very much for your response.
>
>
>
> Attached you can find a grib2. Trying to test this on QGIS (Uses GDAL
> behind), it automatically opens it with  right projection so I guess GDAL
> Will do the same.
>
>
>
> In this file, first grid point should be something like:
>
>
>
> Thank you very much!!
>
>
>
>
>
> *De:* Michael Sumner <mdsumner at gmail.com>
> *Enviado el:* sábado, 3 de septiembre de 2022 8:59
> *Para:* De Juan De España, Javier <jajuan_ext at acciona.com>
> *CC:* gdal-dev <gdal-dev at lists.osgeo.org>
> *Asunto:* EXT: Re: [gdal-dev] Rotated lat lon projection
>
>
>
> First step is try shoving it through the warper:
>
>
>
> gdalwarp in.nc
> <https://clicktime.symantec.com/15t5ZrhtFMk6q5dh8yXpr?h=f3NsNfYLCjuppp90Nv9-oEa-gZU0oRBfBuHIbBwMVFs=&u=http://in.nc>
> out.tif
>
>
>
> set lonlat extent with -te and resolution with -ts or -tr
>
>
>
> GDAL knows about projections and internal coordinate arrays and often this
> is enough, the smart things come down to what output grid you define and
> what resampling algorithm is used and whether it's appropriate (beware of
> vector quantities for example).
>
>
>
> Use a VRT intermediate to first select out one band to test with
> (gdal_translate in.nc
> <https://clicktime.symantec.com/15t5ZrhtFMk6q5dh8yXpr?h=f3NsNfYLCjuppp90Nv9-oEa-gZU0oRBfBuHIbBwMVFs=&u=http://in.nc>
> in1.vrt -b 1). If you have a test file I'm happy to explore.
>
>
>
> Even if the auto stuff doesn't work you can engineer a lot with just
> command line args and VRT even for complex grids.
>
>
>
> Cheers, Mike
>
>
>
> On Thu, 1 Sept 2022, 23:57 De Juan De España, Javier, <
> jajuan_ext at acciona.com> wrote:
>
> Hi!
>
>
>
> We are developping a meteorology project in the Canadian domain where we
> use gdal to manage grib files.
>
> These *files are “rotated lat-lon” and we would like to switch to
> “regular lat-lon”* easily. I’m concerned that lastest versions of gdal
> can do this, but i would really appreciate some indications or information
> about how to do this.
>
>
>
> Thank very much!
>
>
>
> Javier de Juan
>
>
>
>
>
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> *Javier de Juan de España*
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> persona que se ponga en contacto con nosotros por correo electrónico se
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> This e-mail is addressed exclusively to the recipient and may contain
> privileged information under a professional confidential agreement or it
> may be against the law to disclose its contents. Any opinion contained in
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> the company’s view. If you receive this e-mail in error, please let us know
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-- 
Michael Sumner
Software and Database Engineer
Australian Antarctic Division
Hobart, Australia
e-mail: mdsumner at gmail.com
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