[R-sig-Geo] converting raster to netcdf .nc with keeping CRS information

[Ahmed El-Gabbas]

Thanks Ben for your suggestion.

Adding *prj = TRUE *argument caused this error:
           Error in ncdf4::ncvar_def(varname, varunit, list(xdim, ydim),
NAvalue(x),  :
           unused argument (prj = T)

Ahmed

On Tue, Feb 12, 2019 at 3:13 PM Ben Tupper <btupper using bigelow.org> wrote:

> Hi,
>
> Have you tried using the 'prj' argument to writeRaster?  I don't know that
> it will be the solution, but according to ...
>
>
> https://www.rdocumentation.org/packages/raster/versions/2.8-19/topics/writeRaster
>
> It is documented among the '...' arguments.  Setting prj = TRUE will cause
> the crs to be written to the file.
>
> Cheers,
> Ben
>
> On Feb 12, 2019, at 8:34 AM, Ahmed El-Gabbas <elgabass using gmail.com> wrote:
>
> Hello all,
>
> I am having a problem while converting a raster object as NetCDF (.nc)
> file, with keeping the CRS information in the output file.
> Here is a reproducible code:
>
> require(raster)
> require(ncdf4)
> CurrTemp <- tempfile()
> download.file(url = "https://seaice.uni-bremen.de/data/amsre/asi_daygrid_swath/s6250/2003/feb/Antarctic/asi-s6250-20030214-v5.hdf", destfile = CurrTemp, mode = "wb", quiet = T)
> r <- raster(CurrTemp)
> r <- flip(r,2)
> extent(r) <- c(-3950000, 3950000, -3950000, 4350000)
> crs(r) <- "+proj=stere +lat_0=-90 +lat_ts=-70 +lon_0=0 +k=1 +x_0=0 +y_0=0 +a=6378273 +b=6356889.449 +units=m +no_defs"
> r# class       : RasterLayer # dimensions  : 1328, 1264, 1678592  (nrow, ncol, ncell)# resolution  : 6250, 6250  (x, y)# extent      : -3950000, 3950000, -3950000, 4350000  (xmin, xmax, ymin, ymax)# coord. ref. : +proj=stere +lat_0=-90 +lat_ts=-70 +lon_0=0 +k=1 +x_0=0 +y_0=0 +a=6378273 +b=6356889.449 +units=m +no_defs # data source : in memory# names       : layer # values      : 0, 100  (min, max)
>
> So far the raster object reads well, with CRS information included.
> However, when I try to save it as .nc file, R prints "coord. ref. : NA",
> and the produced file does not contain the CRS information.
>
> writeRaster(r, filename = "O:/Ahmed/r001.nc", varname="IceConc",
>             overwrite=TRUE, format="CDF",
>             xname="Longitude", yname="Latitude")# class       : RasterLayer # dimensions  : 1328, 1264, 1678592  (nrow, ncol, ncell)# resolution  : 6250, 6250  (x, y)# extent      : -3950000, 3950000, -3950000, 4350000  (xmin, xmax, ymin, ymax)# coord. ref. : NA # data source : O:/Ahmed/r001.nc # names       : IceConc # zvar        : IceConc
>
> raster("O:/Ahmed/r001.nc")# class       : RasterLayer # dimensions  : 1328, 1264, 1678592  (nrow, ncol, ncell)# resolution  : 6250, 6250  (x, y)# extent      : -3950000, 3950000, -3950000, 4350000  (xmin, xmax, ymin, ymax)# coord. ref. : NA # data source : O:/Ahmed/r001.nc # names       : IceConc # zvar        : IceConc
>
> Any solution?
>
> N.B. I also sent the same question at stackoverflow
> <https://stackoverflow.com/questions/54593552/saving-r-raster-to-netcdf-nc-file-with-keeping-crs-information>,
> without a solution so far.
>
> Thanks
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> *Dr. Ahmed El-Gabbas,*
> Ocean Acoustics Lab,
> Alfred-Wegener-Institut
> Helmholtz-Zentrum für Polar und Meeresforschung
> <image.png>
> My Website:  https://elgabbas.github.io
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>
> Ben Tupper
> Bigelow Laboratory for Ocean Sciences
> 60 Bigelow Drive, P.O. Box 380
> East Boothbay, Maine 04544
> http://www.bigelow.org
>
> Ecological Forecasting: https://eco.bigelow.org/
>
>
>
>
>
>

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