Where is the centre of Ireland?

A new study conducted by Ordnance Survey Ireland challenges historical and mythical views on the true location of the centre of the island of Ireland.

Figure 1: Centre of Ireland

The location of the centre of the island of Ireland has long been disputed.  According to Irish mythology, the centre of Ireland is the Hill of Uisneach, where ceremonial and historic artefacts and monuments have been found dating back to the Neolithic and Bronze Ages.  A six-metre-high limestone rock, known as The Catstone, sits on the side of the Hill of Uisneach and is said to mark the precise centre of Ireland.  Yet, the nearby Hill of Berries, a circular plantation of trees, also lays claim to the title of Ireland’s centre, as does the townland of Carnagh East, County Roscommon.

So where exactly is the mid-point?

According to a new calculation from Ordnance Survey Ireland (OSi), the centre of the island of Ireland actually lies at the Irish Transverse Mercator (ITM) coordinates 633015.166477, 744493.046768, near the community of Castletown Geoghegan, between the towns of Athlone and Mullingar.  This scientifically-calculated centre point is situated, as the crow flies, approximately 31km east of the Hill of Berries, 35km east-south-east of the townland of Carnagh East and a mere 5km south-east of the Hill of Uisneach, Loughnavalley, Co. Westmeath.

Like the Hill of Uisneach, the newly calculated mid-point of the island of Ireland lies on a historical site.  It sits within a National Monuments Zone, on the location of an ancient graveyard and near the remains of Kilbride Church.  Surveyed by the Archaeological Survey of Ireland in 1980, the graveyard today comprises an oval area divided into irregular enclosures and is bordered by the remains of an earth bank and stones.  The church is visible on the first edition of the OS six-inch map from 1837-1842 showing as a rectangular structure with a small transept projecting from the centre of the north wall.

Figure 2: Calculated centre of Ireland, shown on OSi mapping

The calculation to find the exact geographic centre of Ireland was carried out by OSi using the most up-to-date, openly available geospatial data and widely used geographic information system (GIS) technology.  Specifically, OSi used Esri’s Mean Centre Point tool in ArcMap and features data for the Republic of Ireland from its own open-source data set, OSi Admin Areas Ungeneralised, as well as an openly available OSNI Largescale County Boundaries data set from Land & Property Services of Northern Ireland (LPS). The Northern Ireland features were reprojected from an Irish National Grid coordinate system to line up with the OSi features for the republic of Ireland (ITM), enabling the datasets to be processed together.  In just a few short minutes, the coordinates 633015.166477, 744493.046768 were revealed, providing one scientific answer to an age-old question.

Figure 3: OSi map showing the position of the calculated centre and other reputed centre-points

Although carried out by a geospatial specialist at OSi, the calculation to find the centre of Ireland was relatively straightforward.  Any GIS professional with a similar GIS tool could perform a comparable calculation to find the centre of a parish, county or target market, by taking advantage of OSi’s freely available, open-source data.  A government department, for example, might want to find the geographic centre of a catchment area and combine that with demographic information from the census to help it decide where to locate a new school or hospital.  Equally, a commercial business may want to find the centre-point of its service region in conjunction with primary infrastructure information to help identify the best location for a new office or warehouse facility.

Figure 4: First edition OS map from 1837-1842, showing the ecclesiastical setting of the centre-point of Ireland

So, the centre of Ireland is categorically on the old site of Kilbride Church?  Right?

Figure 5: Kilbride Church

Well, maybe.  Even though OSi used the most accurate data openly available and professional GIS technology, there are variables that need to be taken into account.  Most notably, for this exercise, OSi took the conscious decision to exclude the 8,000+ islands and outcrops that encircle the island of Ireland.  If these had been included, this additional data would have affected the shape from which the centre-point was calculated and would inevitably have delivered a slightly different result.  Equally, if the calculation had been based on alternative boundary datasets (with more or less points to calculate from along the coastline, for example) the result could also have been different, and if this exercise is repeated in the future- following erosion and sea level rises, the centre-point could shift again.

Different data processing techniques could also generate different outputs.  A previous study carried out by OSi more than ten years ago, using a different methodology, sited the centre of Ireland 35km away from Kilbride Church, on the western shore of Lough Ree, opposite the Cribby Islands.  In another ten years’ time, advanced technology may tell another story. Perhaps the centre of Ireland could be the Hill of Uisneach after all?

Figure 6: 25 inch historic black and white map from 1888-1913, showing the centre-point in a disused graveyard

The precise location of the centre of Ireland will almost certainly always be a matter for scientific study and popular debate.  Over time, new data, advancing technologies and new techniques could generate different versions of the truth.  For now, though, the site of the ancient Kilbride Church is certainly a credible, scientifically-calculated location of the centre of the island of Ireland.

Figure 7: Latest OSi mapping and imagery at calculated centre

Author: Lauren Lucas, GIS Consultant and Business Analyst, Ordnance Survey Ireland

Find out more!

To explore OSi’s historic maps for yourself, visit  https://geohive.maps.arcgis.com/apps/webappviewer/index.html?id=9def898f708b47f19a8d8b7088a100c4

To learn more about the graveyard and church monuments at the calculated centre-point visit: https://maps.archaeology.ie/HistoricEnvironment/