I have a satellite image with dimensions (11418, 13790, 1). The resolution is 10m. I have two other rasters, which fall inside of my satellite image which are the same resolution and crs.
How would I go about enhancing the extent of small rasters to the size of my satellite image, and then create NA values?
To be clear, I'm looking for a workflow which I think involves changing the extent of my small rasters to the large one using the extent argument and then using the mask function?
Let's make an example with some sample rasters that represent your situation, hopefully. First a big raster with extent from (0,0) to (100,100):
big = raster(matrix(1:100,10,10))
extent(big)=c(0,100,0,100)
Now a small raster spanning part of that from (10,20) to (20,30):
small = raster(matrix(1:100,10,10))
extent(small)=c(10,20,20,30)
Now use extend to expand the bounds of small to the extent of big
smallextend = extend(small, big)
which is this:
class : RasterLayer
dimensions : 100, 100, 10000 (nrow, ncol, ncell)
resolution : 1, 1 (x, y)
extent : 0, 100, 0, 100 (xmin, xmax, ymin, ymax)
crs : NA
source : memory
names : layer
values : 1, 100 (min, max)
Plotting shows smallextend stretching out to the extent of big, but padded with NA values:
Note the extent might not be exact if the resolution doesn't exactly fit into the big raster, for example:
> extent(small2) = c(11.23, 23.7, 22.1, 33.4)
> plot(small2, add=TRUE)
> extend(small2, big)
class : RasterLayer
dimensions : 89, 80, 7120 (nrow, ncol, ncell)
resolution : 1.247, 1.13 (x, y)
extent : 0.007, 99.767, -0.5, 100.07 (xmin, xmax, ymin, ymax)
crs : NA
source : memory
names : layer
values : 1, 100 (min, max)
you can see the output extent isn't quite the same as big because the small2 is not made of 1x1 cells.
