问如何在R中更改栅格图层的分辨率

EN

library(raster)

#get some sample data
data(meuse.grid)
gridded(meuse.grid) <- ~x+y
meuse.raster <- raster(meuse.grid)
res(meuse.raster)
#[1] 40 40

#aggregate from 40x40 resolution to 120x120 (factor = 3)
meuse.raster.aggregate <- aggregate(meuse.raster, fact=3)
res(meuse.raster.aggregate)
#[1] 120 120

#disaggregate from 40x40 resolution to 10x10 (factor = 4)
meuse.raster.disaggregate <- disaggregate(meuse.raster, fact=4)
res(meuse.raster.disaggregate)
#[1] 10 10

from CMD:
gdal_translate -tr 0.1 0.1 "C:\dem.tif" "C:\dem_0.1.tif"

res(raster('C:\dem_0.1.tif')
[1] 0.1 0.1

#
r <- raster("dem.tif")
> res(r)
[1] 0.0002777778 0.0002777778 # original dem resolution
#
r_up_0.1 <- aggregate(r, fact = 0.1/res(r)) # aggregate output
> res(r_up_0.1)
[1] 0.1 0.1
#
s <- raster(nrow = 10, ncol = 10)
extent(s) <- extent(r)
s <- resample(r, s, method = 'bilinear') # resample output
> res(s)
[1] 0.1000278 0.1000278

  #########################################################################
# SubsampleImageRaster.r
#  
# This function demonstrates resampling of raster images to a new
# spatial resolution using the R raster package.
# 
# Author: Rick Reeves
# Date created: 6-October- 2010
# Date modified:                                                             
# NCEAS
#
#########################################################################
#
SubsampleImageRaster <- function()
{
   library(raster)

   sOutFile <- ""
   resampleFactor <- 4  # For test, subsample incoming image by factor of 10

# Read the mosaic components, stored in a subfolder, into a raster object list.
# Within the same loop, obtain the (geographic) extent of each component.
# Note: these images do not have same spatial extent, so they cant be stored
# in a rasterStack. Instead, use a list of rasterLayers.

   setwd("./ForUseCase")
   inFiles <- list.files(pattern="*.tif")
   nFiles <-  length(inFiles)
   inputRaster <- raster()
   CoarseResampRaster <- raster()   
   FineResampRaster <- raster()   
   for (iCtr in 1 : nFiles)
   {
      message(sprintf("resampling file: %s",inFiles[iCtr]))
      inputRaster <- raster(inFiles[iCtr])

# The aggregate() / disaggregate methods resample rasters to COARSER (bigger cells)
# and FINER (smaller cells) resolutions, respectively

      CoarseResampRaster <- aggregate(inputRaster,fact=resampleFactor,fun=mean) 
      sOutFile <- sprintf("CoarseSubsamp%s",inFiles[iCtr]) 
      writeRaster(CoarseResampRaster,filename=sOutFile,format="GTiff",datatype="INT1U",overwrite=TRUE)      
      FineResampRaster <- disaggregate(inputRaster,fact=resampleFactor,fun=mean) 
      sOutFile <- sprintf("FineSubsamp%s",inFiles[iCtr]) 
      writeRaster(FineResampRaster,filename=sOutFile,format="GTiff",datatype="INT1U",overwrite=TRUE)            
   }   

   message("resample demo")
   browser()

# second method: use the resample() method from raster package

# Simple example:
# This code produces a resampled raster, 's',
# with correct resampled values. e.g.; 
# s[] prints a vector of resampled cell values.

   r <- raster(nrow=3, ncol=3)
   r[] <- 1:ncell(r)
   s <- raster(nrow=10, ncol=10)
   s <- resample(r, s, method='bilinear')

# Useful example:
# Resample a satellite image, stored in a GeoTiff file
# into a NEW raster with 2x spatial resolution in 
# both dimensions (four times the number of cells)
# Here is the technique: 
#  1) Create a new raster object with the correct 'resampled' number of cells.
#  2) Set the extent (geographic 'bounding box') of the new raster 
#     to the extent of the original raster
#  3) Generate the resampled raster.

   resampleFactor <- .5  # reduce the cell size by 50% and double the number of rows and columns.      
   inputRaster <- raster("TmB50MosaicImg1.tif")      
   inCols <- ncol(inputRaster)
   inRows <- nrow(inputRaster)
   resampledRaster <- raster(ncol=(inCols / resampleFactor), nrow=(inRows / resampleFactor))
   extent(resampledRaster) <- extent(inputRaster)

# The resample method will write the resampled raster image to a NEW disk file..

   resampledRaster <- resample(inputRaster,resampledRaster,datatype="INT1U",method='bilinear',filename="testOutResamp.tif",overwrite=TRUE)

# Or, use writeRaster method to create the output file.

   writeRaster(resampledRaster,filename="ResampleProduct.tif",format="GTiff",datatype="INT1U",overwrite=TRUE)   


# end
}