"Fathers and Sons"

... IMHO, the location of inter-resource guard posts can always be determined.

Tell me how? I don't always manage to do it. The cell directly below the guard is not checked with a right-click, and if the guard is standing right on the border between different types of terrain, and the cells adjacent to the guard belong to different types (for example, lava to the right and above, and grass below and to the left), then I have to guess 50/50.