Saturday, April 6, 2013

Hidden Landscapes: LiDAR survey allows public to discover new sites

Caithness, in the far northern mainland of Scotland is well known for its spectacular archaeology but a recent LiDAR survey carried in the north of the county has allowed the opportunity to glimpse the wider, hidden landscapes that are less easily appreciated. This survey is beginning to rewrite the history of northern mainland Scotland.

In response to a requirement to record the landscape surrounding the nationally significant cluster of Neolithic chambered cairns at Hill of Shebster, Baillie Windfarm Ltd. commissioned AOC Archaeology Group to carry out a LiDAR survey, the result was stunning and they decided to create a new website to let people explore the ancient landscape hidden beneath fields and woodland in north-west Caithness.

The main focus of the survey was Cnoc Freiceadain, a prominent ridge which is the site of a spectacular group of Neolithic monuments including two long cairns and a series of stone settings.

The 21-turbine project at Baillie Hill, west of Thurso, was granted permission subject to a number of conditions, one of which was to improve public access to the Hill of Shebster and Cnoc Freicedain scheduled ancient monuments, incorporating the results of a LiDAR laser scanning survey.

A billion individual points

LiDAR – which stands for ‘Light Detection and Ranging’ – works by illuminating the ground with laser light and analysing the backscattered light. Modern scanners can fire thousands of laser pulses per second, and by mounting the instrument on an aircraft, large areas can be covered in high resolution in short spaces of time.

Nearly a billion points were collected during the recent LiDAR survey. Once the raw data was gathered it was processed to create very high-resolution elevation models, detailed enough to record field boundaries, walls and ancient monuments – giving an unparalleled view of the archaeology in the area.  Features that are difficult to distinguish on the ground or even through aerial photography can be identified by overlaying hillshades of the DEM model created with artificial illumination from various angles, as with this example.

With LiDAR the ability to produce high-resolution datasets quickly and relatively cheaply is a massive advantage and the ability to penetrate forest canopy has led to the discovery of features that were not distinguishable through traditional methods.

Over 300 new sites

As well as providing spectacular new images of the previously-known monuments around Cnoc Freiceadain the survey has so far revealed over 300 new sites.

The most prominent archaeological features detected by the survey relate to settlement and agriculture dating to around 3000 years ago on one hand, and to post-medieval farming on the other. In many areas, the survey has allowed the identification of palimpsests of agriculture and settlement, where medieval and later rig and furrow systems overlie much earlier cairnfields, interspersed with the fragmentary remains of 3000 year old hut-circles and associated enclosures.

Archaeologist Andy Heald from AOC Archaeology Group said the survey was the first of its kind in the far north of mainland Scotland.

Sites include Sithean Dubh, a chambered cairn where in 1831 it was said two skeletons of “gigantic size” were found.

An opportunity for exploration

This ground-breaking survey offers an unparalleled opportunity for further study of the development of the modern Caithness landscape.

It becomes clear from the LiDAR survey that reanalysis of large parts of Highland Scotland is likely to produce numerous new monuments, and fragments of the prehistoric farming landscape may still remain beneath areas of later activity but unrecognised until this form of survey allows us to view the landscape as a 3D model.

The dataset, therefore, constitutes an invaluable research tool and an unparalleled means of preserving the landscape of 21st century Caithness by record and provides another tool for archaeological research.

One of the main aims of the project was to present the results of the Baillie survey online, in a format that allows different users to explore the data, identify features of interest and explore monuments that are familiar to them.

A dedicated website which showcases the survey results has been produced, linked to the Highland Council’s Historic Environment Record and gives visitors a ‘virtual tour’ of Caithness archaeology.

The website provides information that illustrates the time depth of the land use over thousands of years and becomes a unique window onto Caithness’s past, acting as a valuable resource for archaeological research and interested visitors alike. The archaeologists are already working on the next project to open up data recovered from projects such as this to citizen scientists across the globe.

You can access the web resource and begin your exploration here at www.aocarchaeology.com/Baillie
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References:

Past Horizons. 2013. “Hidden Landscapes: LiDAR survey allows public to discover new sites”. Past Horizons. Posted: February 23, 2013. Available online: http://www.pasthorizonspr.com/index.php/archives/02/2013/hidden-landscapes-lidar-survey-allows-public-to-discover-new-sites

1 comment:

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