Archaeological prospecting in woodland using LiDAR - summary of 2006 surveys

Light Detection And Ranging (LiDAR) surveys are one of our Woodland Heritage Services

About the surveys

During the spring of 2006, LiDAR surveys were undertaken of the forests of Dean and Savernake. The Forest of Dean survey resulted in the largest single heritage survey of a wooded landscape ever undertaken in the UK . Both surveys were commissioned to aid in the discovery, mapping and management of historic environment features.

The two surveys have resulted in hundreds of potentially new features of interest being identified. However, not all of these will be a significant part of the historic environment and many will be modern or false features. Nonetheless, many of these features will be of archaeological significance and the results can be used to target areas for ground-truthing, provide both professional archaeologists and local volunteers with maps for field work in the future. Equally, the models are being used to help forest planners and managers to refine forest design plans and identify sensitive areas prior to forest operations.

The resulting images from the surveys show two very different landscape types as depicted below.

The Forest of Dean

The most striking aspect of the surface model is the evidence for the extensive history of mining and quarrying. Examples of revealed features include many bell pits, quarry faces, rail and trackways, spoil heaps and scowles. Extensive areas of charcoal production are also shown. The images below show examples of the forest canopy and a hillshaded image of the modelled ground surface. Bell pits, quarries and spoil heaps are visible.

  • Aerial photo of forest canopy
    Aerial photo of forest canopy
  • Forest of Dean 2006 LiDAR image
    LiDAR modelled ground surface
  • Forest of Dean 2006 LiDAR image
    Aerial photo of forest canopy
  • Forest of Dean 2006 LiDAR image
    LiDAR modelled ground surface

Savernake

Results from this survey show a different type of landscape. Quarries and pits for mineral extraction are still evident, in addition to the Roman roads and a park pale. The method also shows the remains of World War 2 storage depots, located within the woodland to hide them from aerial reconnaissance, clearly something that is no longer a possibility.

Savernake forest is famous for its collection of veteran trees. The unfiltered (without vegetation removal), last return data can be used in some circumstances to map these trees, where the laser is unable to penetrate the large trunks. This potential is greatest in younger deciduous woodland, as the noisy last return signal from conifer plantations make them more difficult to distinguish.

The images below show parts of the Savernake canopy and the underlying ground model. The park pale, Roman road, quarries and storage depots are visible.

  • Aerial photo of forest canopy
    Aerial photo of forest canopy
  • Savernake 2006 LiDAR image
    LiDAR modelled ground surface
  • Aerial photo of forest canopy
    Aerial photo of forest canopy
  • Savernake 2006 LiDAR image
    LiDAR modelled ground surface