Need for speed: archaeology toolkit
Just as every development scheme is different and presents a unique set of challenges, there is no ‘one size fits all’ approach to archaeological investigations. Part of what we as archaeologists do is to understand the challenges facing our commercial partners and present the right solution.
With an increase in residential housing development, a focus on infrastructure projects and other large sites it’s about picking the right tool from our archaeological toolkit. So what are the available tools and what are their strengths for these kinds of schemes?
As the archaeology profession evolves alongside modern technology our toolkit expands, so this article isn’t a comprehensive rundown of all the available tools (phew), instead it’s a closer look at how certain techniques are being deployed to certain challenges.
Geophysical survey covers a range of techniques that essentially detect buried archaeological remains by measuring physical properties in the ground – no digging required! Magnetometer survey, the most commonly used, is highly effective at identifying features like pits and ditches and is really quick. With favourable conditions many hectares can be surveyed in a day.
We use a large sensor array which is mounted on a cart, together with a GPS antenna which logs our position in real time. This GPS tracking does away with the need to set out large numbers of grid markers across the survey area.
A recent geophysical survey of a site proposed for development close to Hayle, Cornwall, identified a complex of field systems dating from the prehistoric period up to the 19th century. Using these results we designed a targeted programme of trial excavation, the results of which fed into the planning application. The important thing with geophysical survey is that the technology needs to be paired with archaeological expertise to accurately interpret the results and make the best use of this rapid non-intrusive technique.
Handheld laser scanner
This nifty piece of equipment comes into its own when creating plans and cross-sections, whether of buildings or sites, capturing data to a high level of detail and accuracy. The method is speedy so it is particularly useful in large areas or for sites where there are multiple buildings that need recording. We often use our handheld laser scanner in combination with other techniques, from photography to aerial survey.
A recent survey at National Trust property, Canons Ashby, did just that, with the hand held laser survey mapping the interior and exterior of the house. We were able to scan tight roof spaces, often through small access hatches, which would have been difficult and time consuming to undertake with fixed scanners, as well as the large Servant’s Hall. The entire survey of this large building was undertaken in less than two days.
Drone-mounted laser scanner (LiDAR)
Taking laser scanning to the next level, the drone-mounted laser scanner (LiDAR) works by firing a laser at an object, timing how long it takes the pulse to be reflected back, and then converting that time into a distance. The scanner sends out tens or even hundreds of thousands of laser pulses per second to generate a very dense set of 3D spatial points, known as a ‘point cloud’.
Again it’s a rapid technique but it is particularly useful when surveying a site that is wooded because the scanner is able to penetrate through the canopy and reflect the signal off the ground, identifying earthworks and other features hiding beneath the treetops. Take a look at our blog on the drone-mounted laser scanning survey we did of the Badbury hillfort in Oxfordshire.
These are just some of the techniques we employ and in truth projects often benefit from combining techniques to meet the specific challenges presented. Ultimately it is the experts that can advise you on the best techniques for the job and use them to best effect.
If you’d like expert advice on the best approach to your project then please get in touch firstname.lastname@example.org.