On Tue, Nov 7, 2017 at 9:45 PM, Markus Metz <[email protected]> wrote: > > > > On Mon, Nov 6, 2017 at 2:05 PM, Helmut Kudrnovsky <[email protected]> wrote: > > > > Pietro Zambelli wrote > > > Dear Helmut, > > > > > > On 06/11/17 08:22, Helmut Kudrnovsky wrote: > > >> not really an answer, but the data documentation says: > > >> > > >> "Output format: GRIB 1, rotated spherical" > > >> > > >> a quick web search shows some hints to handle such data. > > > > > > Looking at the reference model manual: > > > > > > http://www.cosmo-model.org/content/model/documentation/ core/cosmoDyncsNumcs.pdf > > > > > > at page 25, there are some equation to transform the rotated spherical > > > coordinates back and forward, see the attached image. > > > > > > Are these the hints that you mentioned in your previous reply? > > > > > > Should I convert the raster in to a x_s, y_s, z list of points and write > > > a function to convert the spherical coordinates (x_s, y_s) values > > > defining my own python script to apply the transformation function and > > > generate the lat, lon, z triplet of values, to be imported into a WGS84 > > > location? > > > Any better approach/idea? > > > > > > Thank you for the support. > > > > never used such kind of data for myself; maybe it would be worth to ask on > > the GDAL ML how to used this kind of data. > > GDAL and GRASS use proj4 for reprojection, but proj4 does not support these rotated spheres where the latitude origin for a longlat projection is not 0. The easiest solution is to use a different data source. Otherwise you would have to write a reprojection routine for such rotated spheres. The source code of gdalwarp or r.proj could be used as a template.
The cdo tool [0] can apparently reproject GRIB data from rotated sphere to regular longlat, e.g. with cdo remapcon,outgrid.txt T_2M.2D.201501.grb T_2M.2D.201501.ll.grb where the contents of outgrid.txt are defining the output projection and grid geometry (computational region) with something like --> gridtype = lonlat xsize = 1319 ysize = 610 xfirst = -44.75 yfirst = 21.8333333333333 xinc = 0.0833333333333333 yinc = 0.0833333333333333 <-- with xsize: number of columns ysize: number of rows xfirst, yfirst: lower left corner coordinates xinc, yinc: resolution Markus M [0] https://code.mpimet.mpg.de/projects/cdo/ > > Markus M > > > > some other things I've found in the web, e.g. > > > > https://gis.stackexchange.com/questions/10808/manually- transforming-rotated-lat-lon-to-regular-lat-lon > > https://gis.stackexchange.com/questions/64210/transforming- regular-lat-lon-to-rotated-lat-lon > > http://jgrib.sourceforge.net/docs/rotLatLon.pdf > > [...] > > > > they looks similar you've found. > > > > > > > > > > ----- > > best regards > > Helmut > > -- > > Sent from: http://osgeo-org.1560.x6.nabble.com/Grass-Users-f3884509.html > > _______________________________________________ > > grass-user mailing list > > [email protected] > > https://lists.osgeo.org/mailman/listinfo/grass-user >
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