I want to copy the style of this technical map of a racetrack with Inkscape, but I don't know how to fill a shape with: the bigger and uniform blue dots and the smaller and more diverse blue/green dots (both on the outside of the corner). How could I do that? I imagine it's with the "object to pattern" tool, but every time I try with that the dots are touching each other.
You can do it like this
The crosses are aligned to a square using snapping to centres, then converted from stroke to paths, and unified.
Apply the Intersection boolean operation to the cross pattern and square, and set the fill to the colour you want, and define it as a pattern.
Apply the pattern to a shape, rescale the pattern fill using the control handles (you might need to zoom out to find them)
As for the smaller random dot pattern I don't think you could achieve this with a pattern fill. It looks too random and doesn't seem to repeat in any obvious way. My guess is that it could be a raster image. Note that you can also use a raster image as a pattern in Inkscape.
Something like this perhaps. This was made in GIMP using a texture with diamond shapes that I found online, I added some noise, a threshold adjustment then colourized it.