An aerial laser scan of Bar Hill, one of the forts on the Antonine Wall. LiDAR scans such as this one were able to provide a more accurate measurement of the Roman frontier installation. (IMAGE: Historic Environment Scotland/Canterbury Christchurch University)
A detailed LiDAR survey of the Antonine Wall – the Roman military structure that ran east–west between the Firth of Forth and the Firth of Clyde (see CA 215 and 289) – was recently carried out in a collaborative research project between Canterbury Christ Church University and Historic Environment Scotland. Instead of using the visualisation technology to discover archaeological features, however, the team used these methods to accurately measure the length of the wall in an attempt to solve some long-standing questions about its construction. The project also highlighted the many different ways LiDAR can be used to analyse archaeological sites.
Like other Roman frontier installations, the Antonine Wall had distance-slabs marking its length. Unlike other Roman walls, though, the distance-slabs from the Antonine Wall have detailed descriptions. Twenty slabs have been discovered to-date and while, for the most part, they have increased our knowledge of the wall, they have also created more questions. By measuring the wall more precisely, the team was able to determine such characteristics as the type of measurement used (some of the stones use pes, which could mean either the pes Monetalis or the pes Drusianus – two separate measurements used for the Roman foot), the likely eastern terminus location (Bridgeness or Carriden), as well as the different start and end points used for each construction sector.
The results showed that if we assume the three-dimensional measurements are more similar to the Roman surveyor’s approach than the previous Cartesian measurements (as is likely), the pes Drusianus (0.332m) is a better fit with the LiDAR evidence than the pes Monetalis (0.296m). Additionally, while there has been debate over the eastern terminus of the wall, with Bridgeness being the favoured location as that is where the last distance-slab was discovered, the researchers found that due to the topography of the region, and using the pes Drusianus to determine the distance, Carriden is more likely to have been where the wall ended.
This article appeared in CA 339.