The shape and the positions of the stones relative to each other are unique. It's one of those drawings —an endemic, only found in Serbia— making it possible to determine one's position unequivocally. I agree that GPS would give you a better precision, but also at extra cost because your own eyes and mind would hardly suffice.

The children's signs were also found in Bosnia-Herzegovina. Falling Rocks are maybe also similar, but we can't be sure because we're are still waiting for the first rock signs of that country.