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How to re-project ease( Equal Area Scalable Earth) grid with a ~25 km cylindrical projection to WGS84 0.25 degree?

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How to re-project ease( Equal Area Scalable Earth) grid with a ~25 km cylindrical projection to WGS84 0.25 degree?

Jonsson
This post was updated on .
I have nc files  for global soil moisture,here is one file  https://echange-fichiers.inra.fr/get?k=f9DDllPKdUKs5ZNQwfq

from the metadata ,the projection is cylindrical and the resolution is 25 km(it is based on authalic sphere based on International 1924 ellipsoid).As I want to compare with other data, I have to make them identical.
- my other data are in WGS84 with 0.25*0.25 degree resolution and extent -180, 180, -90, 90.
So I want to re-project  the data I have here
 from
EASE grid, cylindrical,25 km ,1383 pixel  586 lines
 to  
WGS84,0.25*0.25 degree,1440 pixel 720 lines:          
          I tried this:
               
d <-raster("C:\\Users\\aalyaari\\Desktop\\SM_RE01_MIR_CLF31D_20100812T000000_20100812T235959_246_001_7.DBL", varname = "Soil_Moisture")
        d:
        class       : RasterLayer
        dimensions  : 586, 1383, 810438  (nrow, ncol, ncell)
        resolution  : 0.2603037, 0.2916659  (x, y)
        extent      : -180, 180, -85.4581, 85.4581  (xmin, xmax, ymin, ymax)
      coord. ref. : +proj=longlat +datum=WGS84
        names       : Retrieved.soil.moisture.value
           zvar        : Soil_Moisture
       a <- spTransform(d, CRS ("+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs"))
but I got this error:
                 
     Error in function (classes, fdef, mtable)  :
              unable to find an inherited method for function ‘spTransform’ for signature ‘"RasterLayer", "CRS"’        
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Re: How to re-project ease( Equal Area Scalable Earth) grid with a ~25 km cylindrical projection to WGS84 0.25 degree?

Barry Rowlingson
On Fri, Jan 18, 2013 at 5:11 PM, Jonsson <[hidden email]> wrote:

> <-raster("C:\\Users\\aalyaari\\Desktop\\SM_RE01_MIR_CLF31D_20100812T000000_20100812T235959_246_001_7.nc",
> varname = "Soil_Moisture")
>         d:
>         class       : RasterLayer
>         dimensions  : 586, 1383, 810438  (nrow, ncol, ncell)
>         resolution  : 0.2603037, 0.2916659  (x, y)
>         extent      : -180, 180, -85.4581, 85.4581  (xmin, xmax, ymin, ymax)
>       coord. ref. : +proj=longlat +datum=WGS84
>         names       : Retrieved.soil.moisture.value
>            zvar        : Soil_Moisture
>        a <- spTransform(d, CRS ("+proj=longlat +ellps=WGS84 +datum=WGS84
> +no_defs"))
> but I got this error:
>
>      Error in function (classes, fdef, mtable)  :
>               unable to find an inherited method for function ‘spTransform’
> for signature ‘"RasterLayer", "CRS"’
>

 And what is the error telling you? That there's no method for
spTransform that applies to RasterLayers.

 To transform a raster from one projection to another you need to use
projectRaster from the raster package. Note that generally this can
involve warping a raster and interpolating the new values to get a
grid of cells in the new coordinate system.

 But... you were trying to do this:

 a <- spTransform(d, CRS ("+proj=longlat +ellps=WGS84 +datum=WGS84  +no_defs"))

where d was:

 coord. ref. : +proj=longlat +datum=WGS84

 - which is a no-op. The source and destination have the same
coordinate reference system. You need to tell raster what the
coordinate system of the source is. See ?projection - note this
doesn't change the raster or do any projection, its just to tell the
system what the coordinates in the data represent - lat,long or metres
or whatever..

I looked in the HDR file and saw nothing about the projection, so I
don't know how to specify what you've got.

 Also, you didn't point us to the .nc file you used in your example.

Also also, you should probably be posting to R-sig-geo.

Barry

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Re: How to re-project ease( Equal Area Scalable Earth) grid with a ~25 km cylindrical projection to WGS84 0.25 degree?

Jonsson
In fact,it is  netcdf file(even if the extension is DBL). I am new to prjections and i just tried that spTransform,I did not know projectraster. Could you please tell me what is the command using project raster.I wonder if you have tried to re-project the file?
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