I was heading towards suggesting this too.
A fantastic study was done in Sligo by Stefan Burgh and published as a paer called "Landscape of the Monuments".
In this he has taken the lanscape that can be seen from a monument and where it can be seen from. The diagrams are mind blowing. I've never seen a study like it by anyone else, of anywhere else.
This work had a large impact on me. He didn't really prove anything, but the scale of the work is enormous. As I was wondering along discovering cairns and stone rows today I kept thinking along these lines: Why here? Where can I be seen from? Where can I see?
I came across a previously unrecorded pile of stones today. By applying various checkpoints I know have I am fairly confident that it is a genuine cairn.