Calculate the minimum distance of a point grid from the nearest point of another layer with QGIS

Question

I have a grid of 1 km points and a separate group of points representing RTK stations. (See image 1)

I want to create a 3rd value for the grid points that is proportional to the nearest reference station. Something like a mobile coverage map.

The problem is that I don't know how to separate the grid points by closest station and after that don't know how to include the distance between points in calculations. Is a grid of points even the best way to do this, or should I try to create a raster layer?

Answer 1

For each point of the grid layer, calculate the distance to the closest point of the layer named RTK with this expression:

length(
    make_line(
        $geometry, 
        overlay_nearest('RTK',$geometry)[0]
    )
)

Point label and color of points based on the expression above: