Using GIS to Locate Bere Island’s Napoleonic Defences

As the date of our survey on the Napoleonic-era defences of Bere Island nears, we are busy in the Rubicon offices preparing mapping for each of the sites. One of our key tools in this is the use of GIS, which is short for Geographical Information Systems.

Martello Tower No.4 and Battery No. 4, Ardagh, Bere Island. This screenshot shows the 1st edition map of the positions with the GIS 'trace' overlaid, which will then be fed into the GPS for use in the field.

Martello Tower No.4 and Battery No. 4, Ardagh, Bere Island. This screenshot shows the 1st edition map of the positions with the GIS ‘trace’ of key features overlaid, which will then be fed into the GPS for use in the field.

GIS is a key part of our survey, as it will allow us to quickly and accurately identify where the early 19th century defences stood. Using this computer software, we overlay the 19th century mapping on 21st century maps for each of the sites. This allows us to geographically locate each of the original elements of the site with pinpoint accuracy. We then upload outlines drawn from the old maps into our GPS (Global Positioning System) survey equipment which in the field can virtually ‘show us’ where everything was, according to the 1830s mapping. When we travel to a position such as the Ardagh Gun Battery, our GPS Rover allows us to mark out where the original limits of the building were 170 years ago, and even where field boundaries and ordnance stones were placed.

Rerrin Village as it appeared at the time of the first Ordnance Survey. Military and domestic buildings have been 'traced' in GIS, which will allow us to discover on the ground how the village has changed in the last 170 years.

Rerrin Village as it appeared at the time of the first Ordnance Survey. Military and domestic buildings have been ‘traced’ in GIS, which will allow us to discover on the ground how the village has changed in the last 170 years.

Using GIS combined with GPS in this way allows us to understand how a site has changed since the 1830s ( is the field boundary still there? have the ordnance stones moved? does the military road still exist?), if a site has been destroyed we can see where on the ground it once stood and if there are any traces remaining (such as at Martello Tower No. 1, which was later replaced by the Lonehort Battery), examine how accurate the original mapping was (are there additional features not shown on the old mapping that are visible, such as the Ardagh Battery gun positions?) and locate areas of the site that may now be obscured (e.g. overgrown with bushes or gorse). This is a major component of our survey methodology, and something volunteers will become familiar with over the course of the two weeks in the field. Excitement is building as the survey dates approach!

Martello Tower No. 1 and Battery No. 1, Bere Island. These sites were destroyed by the later Lonehort Battery, but by using our GIS 'trace' of the original locations we can go to the site of their original locations and see if any traces of either structure survive.

Martello Tower No. 1 and Battery No. 1, Bere Island. These sites were destroyed by the later Lonehort Battery, but by using our GIS ‘trace’ of the original locations we can go to the site of their original locations and see if any traces of either structure survive.

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1 Comment

  1. Nice work. The U.S. National Park Service is using GIS/GPS with historic maps in the same way to survey the Civil War Defenses of Washington. We were able to find resources at several sites that we did realize were there. Military cartographic engineers were indeed capable individuals, and their maps should not be downplayed as useful historic source materials.

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