The maps seems to suggest broadly that the underlying geology plays a big factor in where they are located. I think the underlying geology may also have been a factor in the location of some of the county boundaries also. It may be tricky to read because of all the different soil / geology types represented. The map is based on information from the National Monument Service of Ireland, Department of Communities - Northern Ireland Sites & Monuments Record, the Geological Survey of Ireland & Open Street Map Ireland contributors.
My blog looks at the archaeology and heritage of sites in Tipperary and surrounding areas. As many of these sites are on private property, it is important to request permission from the landowner before entering private lands so that access does not become a problem across all sites.