Over the past three days I've read several posts, at least one of them highly enthusiastic, about the website for the Down Survey of Ireland.
According to the site description:
There are two main components to this website. The Down Survey Maps section comprises digital images of all the surviving Down Survey maps at parish, barony and county level. The written descriptions (terrier) of each barony and parish that accompanied the original maps have also been included. The second section, Historical GIS, brings together the maps and related contemporaneous sources – Books of Survey and Distribution, the 1641 Depositions, the 1659 Census – in a Geographical Information System (GIS). All these sources have been georeferenced with 19th-century Ordnance Survey maps, Google Maps and satellite imagery.It may well be that I don't have enough Irish ancestry, or know the ancestry far enough back, for it to be useful for me. I'm not the only one. Perhaps you'll be more fortunate.