spTransform changes the class

spTransform cannot reproject a grid - this will (usually) requires
destructive resampling of the data to a completely new grid. There are
functions in the raster package to do this: projectRaster.

I think this would work, but there may be important details that you
will need to investigate:

raster.eugrd025 <- raster(eugrd025)

eugrd025EFDC <- projectRaster(raster.eugrd025,
CRSobj=CRS(projection(eugrd025EFDC_SPDF)))

On Fri, Jul 2, 2010 at 1:40 AM, Agustin Lobo <alobolistas at gmail.com> wrote:

Hi!

I use spTransform to reproject:

class(eugrd025)

[1] "SpatialGrid"
attr(,"package")
[1] "sp"

projection(eugrd025)

[1] "+proj=longlat +ellps=WGS84"

eugrd025EFDC <- spTransform(eugrd025, CRSobj=CRS(projection(eugrd025EFDC_SPDF)))

projection(eugrd025EFDC)

[1] "+proj=laea +lat_0=52 +lon_0=10 +x_0=4321000 +y_0=3210000
+ellps=GRS80 +units=m +no_defs"

This is good, but:

class(eugrd025EFDC)

[1] "SpatialPoints"
attr(,"package")
[1] "sp"

Why is the class changed to SpatialPoints? I need a grid object for

eugrd025EFDCr <- raster(eugrd025EFDC)
Br025 <- resample(Br,eugrd025EFDCr)

don't I?

I also have the problem that the CRS of eugrd025EFDCr is not conserved:

projection(Br)

[1] "+proj=laea +lat_0=52 +lon_0=10 +x_0=4321000 +y_0=3210000
+ellps=GRS80 +units=m +no_defs"

projection(eugrd025EFDC)

[1] "+proj=laea +lat_0=52 +lon_0=10 +x_0=4321000 +y_0=3210000
+ellps=GRS80 +units=m +no_defs"

projection(eugrd025EFDCr)

[1] "NA"

which I fix with

projection(eugrd025EFDCr) <- CRS(projection(eugrd025EFDC))

and repeat

Br025 <- resample(Br,eugrd025EFDCr)

Anyway, I get a much coarser raster than I want:

dim(Br025)

[1] 10 10 ?1

because

dim(eugrd025EFDCr)

[1] 10 10 ?1

While it should be 180x100:

summary(eugrd025EFDC)

Object of class SpatialPoints
Coordinates:
? ? ? min ? ? max
s1 2498538 6561151
s2 1327858 4313263
Is projected: TRUE
proj4string :
[+proj=laea +lat_0=52 +lon_0=10 +x_0=4321000 +y_0=3210000 +ellps=GRS80
+units=m +no_defs]
Number of points: 18000

dim(Br025)

[1] 10 10 ?1

summary(eugrd025)

Object of class SpatialGrid
Coordinates:
? ? ? ? ? ? ?min ? ?max
coords.x1 -10.125 34.875
coords.x2 ?34.875 59.875
Is projected: FALSE
proj4string : [+proj=longlat +ellps=WGS84]
Number of points: 2
Grid attributes:
?cellcentre.offset cellsize cells.dim
1 ? ? ? ? ? ? ? -10 ? ? 0.25 ? ? ? 180
2 ? ? ? ? ? ? ? ?35 ? ? 0.25 ? ? ? 100

Is eugrd025EFDCr wrong because class(eugrd025EFDC) has been changed
from SpatialGrid to SpatialPoints?

Agus