Aerial Archaeology in Ireland - The Heritage Council

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shoreline and topography (ground elevations) simultaneously, integrating land and water measurements in the same data set.
Submerged wrecks, structures and other objects (down to 2m x 2m x 2m dimensions) have been recorded. Based in the UK,
Admiralty Coastal Surveys is another group involving the UK Hydrography Office which offers coastal and marine airborne
bathymetry using lidar.
The Use of Lidar in Ireland
An important study commissioned by the Heritage Council has examined the value of lidar coupled with conventional imagery
and field survey in the Loughcrew area. More recently, the OSi have undertaken a detailed lidar survey of the Rathcrogan
complex and BKS Ltd has undertaken a survey of Newtown Jerpoint, Co. Kilkenny, for the Heritage Council and the Discovery
Programme (Figure 28). The value of lidar for marine archaeological survey is also being developed.
The Loughcrew study was undertaken by Colin Shell and Corrine Roughley of the University of Cambridge in conjunction with
Elizabeth Shee Twohig of the University of Cork (Shell and Roughley 2004; Shell et al. 2004). They applied lidar scanning to a 5x6km
core area (83 million points measured in 25 swathes) within a wider 10x12km area covered by conventional photogrammetry
(65 vertical photographs taken for the purpose at a scale of 1:12,500), tied in to 101 ground control points tied in to the Irish
National Grid through GPS and OSi data. The photographic coverage was ortho-rectified and mosaicked into a continuous,
colour rectified image. Using GIS, both the lidar and photogrammetric images could be combined and manipulated and overlaid
with historic map evidence and archaeological data available from the SMR. The results have clearly demonstrated the value
of the technique for archaeological site identification and analysis, in addition to understanding at the landscape scale even
in an area that is already well-known and has been intensively surveyed. About 160km of linear archaeological features were
analysed and digitised from the lidar data, only 10% of which were previously included as Recorded Monuments. In addition,
new discoveries include: three possible barrows and 13 other round mounds; three larger mounds and five sub-circular banks;
four square mounds; and a substantial moated site (Figure 30).
The GSI and the Marine Institute have commissioned a lidar survey for Stage 2 of the Irish National Seabed Survey over three
years (2006-9). Key bays and priority areas around Ireland have been targeted for integrated survey work. The areas were
selected after intensive consultation through the various stakeholders, including the Underwater Archaeology Unit of DoEHLG.
Included within the priority bays are areas that have high archaeological potential (i.e. piers, harbours, fish traps and wreck sites).
Where possible, airborne lidar has been selected as the preferred tool for mapping the inshore areas. Following the successful
location and mapping of wrecks in shallow waters off Donegal using lidar and side-scan sonar, the results of these surveys are
likely to be of significant interest for coastal and inshore underwater archaeology. The programme will be reviewed at the end
of the three years.
So far, the direct application of such techniques to archaeology has been inhibited by the relatively high cost of new survey
imagery. The availability of specialists able to process the data can also prove problematic, as is the lack of general coverage
of the country at suitable levels of resolution. Despite the undoubted quality of outputs (which in many respects exceed
what is available through conventional photography), these issues remain significant barriers to the more general use of lidar.
However, this is likely to change rapidly as the technology and its availability improve and costs are reduced. Perhaps even more
pertinently, further rapid change is likely as the value of integrating archaeology with other objectives becomes more widely
appreciated.