Smoothing rasters


Sometimes it is helpful for visualization purposes (or when making a nice graphic), to smooth out a raster image. Here are some cheap and quick methods.

Rodney Dyer (Center for Environmental Studies)

So let’s load in a raster and crop it down to look at it. Here is the area surrounding Loreto, BCS Mexico as represented by a 1-km resolution raster of elevation.

library( raster )
url <- ""
raster( url ) %>%
  crop(extent( -111.6, -111, 25.6, 26.2) ) -> baja_california
plot( baja_california ) 

For simple viewing, we can tell the plot to interpolate it, which will shape it a bit. This does not change the data, it only shows the data a bit differently.

plot( baja_california, interpolate = TRUE )

We can also resample the data, which changes it. We can disaggregate it, which makes a new raster with a more fine grain resolution and interpolates the new values to fit.

loreto_disaggregated <- disaggregate( baja_california, 
                                      fact = 5,
                                      method = "bilinear")

which takes the previous raster whose size was:

dim( baja_california )
[1] 72 72  1

and makes the new one of size

dim( loreto_disaggregated )
[1] 360 360   1

as the fact=5 means that each cell in baja_california is turned into a 5x5 set of cells whose values are interpolated. Notice in the plot below, how the pixelation is reduced around the coast (this raster has all water = NA).

plot( loreto_disaggregated )

We can also smooth it using a custom focal operation based upon a matrix of values and a function we define for it. Here the weight (w) matrix is a 5x5 matrix of 1 (defining the values around each spot that will be used) and the fun=mean will take the average of the 5x5 matrix of values.

loreto_focal <- focal( baja_california, 
                       w = matrix(1, 5, 5), 
                       fun = mean, 

This approach does not change the resoution of each cell, it only smooths it out. I also ignored NA for those edge cases.

dim( loreto_focal )
[1] 72 72  1

And if you look at it, it still has some pixelation (minecraft-i-ness if you will)

plot( loreto_focal )

The method you choose is up to you and the consequences of changing the raw data. Be careful.


For attribution, please cite this work as

Dyer (2021, Dec. 15). The Dyer Laboratory: Smoothing rasters. Retrieved from

BibTeX citation

  author = {Dyer, Rodney},
  title = {The Dyer Laboratory: Smoothing rasters},
  url = {},
  year = {2021}