Hello,
I have two rasters with different resolution and projection.
> r1
class : RasterLayer
dimensions : 2510, 5233, 13134830 (nrow, ncol, ncell)
resolution : 56, 56 (x, y)
extent : 503198, 796246, 4917498, 5058058 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=utm +zone=18 +datum=WGS84 +units=m +no_defs +ellps=WGS84
+towgs84=0,0,0
data source : in memory
names : layer
values : 1, 8 (min, max)
> r2
class : RasterBrick
dimensions : 3250, 6570, 21352500, 1 (nrow, ncol, ncell, nlayers)
resolution : 30, 30 (x, y)
extent : 265380.5, 462480.5, 4984457, 5081957 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=tmerc +lat_0=0 +lon_0=-73.5 +k=0.9999 +x_0=304800 +y_0=0
+ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
data source : H:\users\rast_temp.tif
names : rast_temp
My objective is to merge the two rasters into a single raster. As the two
rasters have different resolution and projection, I have used the function
projectRaster (package raster) like this:
r <- projectRaster(from=r1, to=r2, method="ngb", alignOnly=TRUE)
However, I got this warning message:
Warning message:
In projectRaster(x, crs = projection(y)) : 'from' has no cell values
and yet, the two rasters have values:
> hasValues(r1)
[1] TRUE
> hasValues(r2)
[1] TRUE
When I remove the argument "alignOnly=TRUE", the code seems to work but I don't
want that r1 has the same projected extent than r2 (I want to keep the original
extent of r1).
Why do I get this warning message ?
Thank you very much for your help.
Marine
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