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Lidar

Hambledon Hill - lidarAirborne lidar (Light Detection And Ranging) measures the height of the ground surface and other features in large areas of landscape with a resolution and accuracy hitherto unavailable, except through labour-intensive field survey or photogrammetry. It provides, for the first time, highly detailed and accurate models of the land surface at metre and sub-metre resolution.

Lidar operates by using a pulsed laser beam which is scanned from side to side as the aircraft flies over the survey area, measuring between 20,000 to 100,000 points per second to build an accurate, high resolution model of the ground and the features upon it. For further details of the technology see the Unit for Landscape Modelling - Cambridge University (ULM) or the Environment Agency (EA).

Airborne lidar was conceived in the 1960’s (for submarine detection), and early models were used successfully in the early 1970’s in the US, Canada and Australia. In the United Kingdom the Environment Agency has for several years used lidar for the production of cost-effective terrain maps suitable for assessing flood risk. They have data for large areas of the country, concentrating on the coasts and river valleys and this is available for use by legitimate researchers subject to strict licensing agreements, an example of which can be found attached below. In more recent years many other bodies have acquired the capability to carry out lidar surveys and it is used regularly by utilities companies, highway agencies etc.

Newton Kyme - lidarThe possibilities of lidar for archaeological recording were first recognised at a NATO sponsored workshop to discuss future practices in aerial archaeology, held in Leszno, Poland in November 2000, where a survey covering the River Wharfe in Yorkshire revealed evidence for the earthwork survival of a Roman fort that had previously been thought to have been completely levelled by ploughing.

Following on from this and recognising the potential for lidar to record very slight earthwork remains English Heritage contracted the Environment Agency to fly a survey of the Stonehenge World Heritage Site and has since worked with both the Environment Agency and the Unit for Landscape Modelling looking at different areas of the country with varying levels of monument survival. They have also been closely involved working with ULM looking at the potential for lidar to penetrate wooded terrain.

English Heritage are looking at the best ways to utilise the lidar data for archaeological purposes and also working with other users of lidar and other laser scanned data in a forum called Heritge3d to develop best practice for data recording and storage.

PDF file Environment Agency Data Licence Agreement get Acrobat  This document requires Adobe Acrobat Viewer to display. This free software is available from Adobe. Download Acrobat here

Recent projects using lidar

  • Charterhouse lidar thumbnail
    Mendip Hills lidar
    The Mendip Hills AONB NMP project is the first project where lidar data is being examined simultaneously with standard aerial photographs. The Mendip landscape is largely pasture and so it is hoped that lidar will be able to record slight earthwork features that would not otherwise be visible.
  • Savernake lidar thumbnail
    Savernake Forest lidar
    A significant element of the Savernake Forest NMP project was the examination of lidar data in the hope of identifying features hidden beneath the forest canopy.
  • Stonehenge lidar button
    Stonehenge WHS lidar
    The Stonehenge lidar survey had its origins in the requirement for English Heritage and the National Trust to produce a management plan for the World Heritage Site at Stonehenge, and an archaeological response to the improvements to the roads around Stonehenge. The Stonehenge landscape is one of the most studied in Europe so if the new lidar technique proved useful here it was likely to have similar or greater impact for other historic landscapes.
  • Barlings lidar thumbnail
    Witham Valley lidar
    As part of the broader Witham Valley NMP project the opportunity was taken to access the lidar data of the area flown by the Environment Agency in 2001. Analysis revealed not only useful data about the geomorphology of the project area, but also provided evidence for previously unrecorded sites. In addition it was a useful exercise in the potential risks of using single sources of data for interpretation.

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