A new website, which brings a unique 17th-century map collection together for the first time in 300 years as a public online resource, is being launched in Trinity College Dublin this evening.

The Down Survey website maps out for the first time in great detail the dramatic transfer in landownership from Catholics to Protestants.

The resource will give a greater understanding of 17th-century Ireland.

The Down Survey of Ireland, undertaken by the Cromwellian regime in the years 1656-1658, introduced modern mapping techniques to Ireland, creating the first recognisable maps of the country.

It was also the first ever detailed land survey on a national scale anywhere in the world and measured all the estates to be forfeited by Catholic landowners.

This collection, the originals of which were destroyed in two fires in 1711 and at the Four Courts in 1922, comprises county, barony and parish maps.

It is rich in detail, showing not only townland boundaries, but also churches, roads, rivers, bogs, woods and settlements.

Led by Dr Micheál Ó Siochrú, Associate Professor in Modern History, TCD historians have now tracked down over 2,000 contemporaneous copies of the original survey maps in dozens of libraries and archives throughout Ireland, Britain and France.

They have brought them together as a free online resource.

By overlaying these maps onto Ordnance Survey maps and Google maps, and employing geographic information system technology, the website allows users to explore this turbulent period in Irish history to an extraordinary level of detail.

Key features of the website include:

- 2,000 county, barony and parish maps from the Down Survey

- National, provincial and county maps detailing massive landownership transfer

- Mapping out of murders and violent assaults reported during the 1641 rebellion

- Representation of 17th-century road network

- A searchable database of over 10,000 landowners

Speaking in advance of the launch, Dr Ó Siochrú said: "The Down Survey website is an extraordinary and unique resource for early modern Irish history, which will absolutely transform our understanding of 17th century Ireland.

"Preliminary research based on ongoing work suggests that our understanding of the scale and timing of the massive transfer of land from Catholic to Protestant landholders will need to be reassessed."

"The bringing together of this highly detailed map collection and related contemporaneous material with the aid of GIS technology allows us to reconstruct this period of Irish history.

"It will be of great interest to historians, genealogists, sociologists, engineers and anyone with an interest in Ireland, its past and its people."