Griffith's Valuation (GV) collection.
Since 2003, this GV collection has been available only on Irish Origins, now a sister company of FindMyPast.ie in the DC Thompson Family History stable.
It was developed by the National Library of Ireland, Eneclann and OMS Services and brought together 300 of the 301 GV publications dispersed across the National Library, the National Archives, the Valuation Office, the Genealogical Office, the Gilbert Library, the private collection of George Handran and other archives.
The information was then digitised and made fully searchable (by person and placename) to create what is widely accepted as the most comprehensive version of Griffith's Valuation online.
The Ordnance Survey (OS) maps and town plans used by the team working on Griffith's Primary Valuation during 1847-1864 still exist, marked up and annotated by those working on the Primary Valuation and subsequently by Valuation Office personnel. For many places there are multiple plans, usually created at different times, and these are easily accessible when viewing the images. The majority are undated, but the one you retrieve when searching the FindMyPast collection will usually be the earliest ie the one first used in Griffith's Valuation.
Unfortunately, the FindMyPast collection does not have maps, only transcripts, for the six counties of Northern Ireland (Antrim, Armagh, LondonDerry, Down, Fermanagh and Tyrone).