[GRASS-user] Creating mapset and/or importing data based on a proj4 string

[Ken Mankoff]

Dear Moritz and Helmut,

Thank you for letting me know that the GRASS GUI (and g.proj) have the
ability to work directly with proj4 strings.

  -k.

On Fri, Oct 6, 2017 at 10:34 AM, Helmut Kudrnovsky <hellik at web.de> wrote:

> Ken Mankoff wrote
> > Dear List,
> >
> > Most of the time when I work with data in GRASS it is a provided on a
> > standard GIS grid (EPSG code) and I can work with it easily. I create a
> > location using the "-c" option when I start GRASS, or I import it into an
> > existing mapset with r.import.
> >
> > I'm now working with data and all I know is this:
> >
> > +proj=stere +lat_0=90 +lat_ts=71 +lon_0=-39 +k=1 +x_0=0 +y_0=0
> > +datum=WGS84
> > +units=m +no_defs”
> >
> > In the past, when working with a few variables and this information, and
> > lat/lon grids in the NetCDF file, I would export the data (using Python)
> > to
> > lat,lon,data, and then r.in.ascii and project it that way. However, now
> > I'm
> > working with 14,000 high resolution daily records on the above
> projection.
> >
> > It seems the only way to do this efficiently is to work in the projection
> > of the data, and r.import the few other variables to this projection. Or
> > perhaps cdo or gdal or some other 3rd party tool can quickly re-project
> > everything for me to a known EPSG code. I've solved this before with
> > vectors, ogr2ogr, and arbitrary proj4 strings.
> >
> > Can anyone here suggest how to best get this data into GRASS?
> >
> > I've tried using gdalwarp:
> >
> > gdalwarp -of GTIFF -s_srs "+proj=stere +lat_0=90 +lat_ts=71 +lon_0=-39
> > +k=1
> > +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs" -t_srs EPSG:3413
> > NETCDF:"${file}":RU out.tif
> >
> > But am concerned because when I then run gdalinfo on the out.tif file, it
> > reports strange bounds such as:
> >
> > Origin = (-909.965548780931840,1546.900601999830769)
> > Pixel Size = (7.477558376763198,-7.477558376763198)
> > Corner Coordinates:
> > Upper Left  (    -909.966,    1546.901) (165d27'58.34"E, 89d59' 0.36"N)
> > Lower Left  (    -909.966,   -1264.661) ( 80d44'10.54"W, 89d59' 8.22"N)
> > Upper Right (     794.918,    1546.901) (107d48' 8.56"E, 89d59' 2.20"N)
> > Lower Right (     794.918,   -1264.661) ( 12d50'53.17"W, 89d59'10.36"N)
> > Center      (     -57.524,     141.120) (157d10'37.34"E, 89d59'54.94"N)
> >
> > Which seems to be very close to the pole (both lower and upper at >89
> > deg).
> > This should be covering a much large portion of the Arctic.
>
> e.g. you can use a proj4 string in the startup wizard to create a new
> location.
>
> just tested with your proj4 string,
>
> g.proj -j
> +proj=stere
> +lat_0=90
> +lat_ts=71
> +lon_0=-39
> +k=1
> +x_0=0
> +y_0=0
> +no_defs
> +a=6378137
> +rf=298.257223563
> +towgs84=0.000,0.000,0.000
> +to_meter=1
>
> HTH
>
>
>
> -----
> best regards
> Helmut
> --
> Sent from: http://osgeo-org.1560.x6.nabble.com/Grass-Users-f3884509.html
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