R：如何通过应用具有（大）宽度的高斯滤波器来增加卫星图像的像素大小（降低空间分辨率）

Question

The goal

I am trying to simulate coarse data as though they were measured with a coarse PSF (point spread function).

The data

I have a satellite image with 15m pixel size and I want to convolve it with a Gaussian kernel to reduce the spatial resolution at 460m. To do this I need to apply a transfer function (TF; eg, Gaussian) to the fine data, but with a very large width. This produces the coarse data.

Is there any function that takes as input a fine resolution image, applies a Gaussian TF and produces a coarse spatial resolution image?

To make my problem even more clear, I am following the paper ' The effect of the point spread function on downscaling continua '. All in all, the authors wanted to downscale a coarse satellite image using an ancillary fine spatial resolution variable. The downscaling consists of two steps:

1. regression
2. kriging on regressions residuals

During the regression, they had to upscale the fine resolution image to match the pixel size of the coarse resolution image and then they performed the regression. This upscaling had to be done using the PSF .

From here you can download my image.

Answer 1

Based on the this question , the code of the person who invented the method Area-to-point regression Kriging, Qunming Wang, and the description of the function down_sample_image from the OpenImageR package, I managed to upscale the image using a Gaussian blur . All in all, I had to multiply the PSF * the zoom factor .

library(raster)
library(OpenImageR)

r = raster("path/tirs.tif")

m = as.matrix(r)

psf = down_sample_image(m,
                        factor = 4.6, # zoom factor
                        gaussian_blur = T,
                        gauss_sigma = 0.5 * 100) # sigma * pixel size

e <- extent(r)

m2r <- raster(psf)
extent(m2r) <- e
raster::crs(m2r) <- "EPSG:7767"
res(m2r)

writeRaster(m2r, "path/tirs460.tif")