[R-sig-Geo] How to upscale (reduce the spatial resolution) an image using a Gaussian filter in R?

[Greg Snow]

The `image_resize` function in the `magick` package may be a simple
option.  A gaussian filter is one of the options.  This uses the
ImageMagick program behind the scenes, but is a quick and easy
interface within R for images (raster data).

On Tue, Sep 6, 2022 at 10:46 AM Nikolaos Tziokas
<nikos.tziokas using gmail.com> wrote:
>
> Hi,
>
> I want to resample a raster from 15m to 460m (pixel size) using a Gaussian
> filter.
>
> *The goal*
>
> I am having a coarse image which I want to downscale. I also have a fine
> resolution band to assist the downscaling. The downscaling method I am
> using is called geographically weighted area-to-point regression Kriging
> (GWATPRK). The method consists of two steps:
>
>    1. GWR
>    2. area-to-point Kriging on the GWR's residuals
>
> In order to perform GWR using raster data, those needs to have the same
> pixel size. This means that, my fine resolution image needs to be upscaled
> to match the spatial resolution of the coarse band. This upscaling of the
> fine band needs to be done using a Gaussian kernel with σ=0.5(i.e., the
> PSF).
>
> How can I upscale (reduce the spatial resolution) a satellite image using a
> Gaussian kernel (i.e., point spread function)?
>
> For reference, I am following the paper The effect of point spread function
> on downscaling continua
> <https://www.sciencedirect.com/science/article/pii/S092427162030229X> where
> the authors at p.253 in Eq (9) mention:
>
> *the coarse image produced by upscaling the corresponding fine band k using
> a PSF.*
>
> I googled how I can achieve that but unfortunately I couldn't find any
> solution. So to do this, how can I use this Gaussian filter to change the
> resolution (pixel size) of my image?
>
> Here is the image
> <https://drive.google.com/drive/folders/18_1Kshb8WbT04gwOw4d_xhfQenULDXdB?usp=sharing>
> I
> am trying to convolve.
>
>
> Many thanks
>
>
> --
> Tziokas Nikolaos
> Cartographer
>
> Tel:(+44)07561120302
> LinkedIn <http://linkedin.com/in/nikolaos-tziokas-896081130>
>
>         [[alternative HTML version deleted]]
>
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-- 
Gregory (Greg) L. Snow Ph.D.
538280 using gmail.com