International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-5/W2, 2013
XXIV International CIPA Symposium, 2 — 6 September 2013, Strasbourg, France
REVEALING THE SECRETS OF STONEHENGE THROUGH THE APPLICATION OF
LASER SCANNING, PHOTOGRAMMETRY AND VISUALISATION TECHNIQUES
P.G. Bryan' *, M. Abbott ^ AJ. Dodson
*English Heritage, 37 Tanner Row, York YO1 6WP, UK - paul.bryan(genglish-heritage.org.uk
? ArcHeritage, 54 Campo Lane, Sheffield, S1 2EG, UK - mabbott@yorkat.co.uk
* Greenhatch Group Ltd, Duffield Road, Little Eaton, Derby, DE21 5DR, UK - andrewd@greenhatch-group.co.uk
*Corresponding author
Commission V, Working Group V/2
KEY WORDS: Laser Scanning, Photogrammetry, Surveying, Visualisation, Cultural Heritage, Archaeology
ABSTRACT:
Stonehenge is perhaps the most famous prehistoric monument in the world. Begun as a simple earthwork enclosure, it was built in
several stages with the unique lintelled stone circle being erected in the Neolithic period in around 2,500 BC. Today Stonehenge,
together with Avebury and other associated sites, form the heart of a World Heritage Site (WHS) with a unique and dense
concentration of outstanding prehistoric monuments. In 2011 English Heritage (EH) embarked on a new survey of the monument.
Undertaken by the Greenhatch Group, a commercial survey company based near Derby, a combination of laser scanning and
photogrammetric approaches were used to generate the required scale and detailed level of output required by English Heritage. This
paper will describe the background to this project and its context within previous survey activities at this World Heritage Site. It will
explain the data acquisition technology and processes undertaken on site, the datasets derived from post-processing and their filtering
and analysis within both subsequent research projects. Alongside a description of how the data is currently being exploited and
proposed future applications within the conservation and management of the site, it will finish by considering the impact of
developing geospatial imaging technologies.
1. INTRODUCTION photography, topographic and elevational survey all stored
within the Historic Plans Room and accessible to both internal
Stonehenge is perhaps the most famous prehistoric monument staff and the general public through EH's Enquiry & Research
in the world (Figure 1). Services team. The last detailed survey of the monument was
undertaken using photogrammetry in 1993 by the York-based
Photogrammetric Unit. Film-based stereo-photography captured
on site, controlled by theodolite observations to multiple fixed
targets, was processed using the Leica Helava Digital
Photogrammetric Workstation to provide three dimensional
surface models for each of the stones at a resolution of 2cm
(Bryan et al, 1997). Laser scanning had only previously been
applied on a trial basis at the site such as that undertaken by
Wessex Archaeology and Archaeoptics in 2002/2003 (Goskar
et al, 2003). Using a Minolta VI-900 structured light scanner,
surface data to 0.5mm resolution was captured for three stones
and, using a combination of visualisation techniques, new
carving information revealed. Although only applied to a
fraction of the monument this still highlighted the great
potential of applying modern scanning systems across all the
standing and fallen stones that comprise Stonehenge.
Figure 1 The site of Stonehenge viewed from the air (Image by
Damian Grady, 1504122 O English Heritage) 1.2 Stonehenge Landscape Survey
Begun as a simple earthwork enclosure, it was built in several In 2007 English Heritage embarked upon an analytical
stages with the unique lintelled stone circle being erected in the landscape survey of the Stonehenge WHS at various levels of
Neolithic period around 2,500 BC (Bryan, 2011). Inscribed asa detail and scale (Field et al, 2010). Known as the Stonehenge
World Heritage Site (WHS) in 1986 for its outstanding Landscape Survey this would use a range of techniques,
prehistoric monuments, the Stonehenge part of the WHS covers including plane-table and GPS survey, to map and enhance
2,600 hectares and is managed by several landowners including existing understanding of both the earthworks and upstanding
English Heritage (EH) and the National Trust. remains across the WHS landscape. Although
photogrammetrically derived data already existed on the henge
1.1 Existing survey it was felt its’ centimetre resolution was now insufficient for
detailed archaeological analysis and would therefore limit
A wide variety of survey material already exists for the site future potential for revealing new surface information. In
held within the English Heritage Archive (EHA), located 56 km addition the announcement in 2009 of a new visitor centre for
north in Swindon. This includes aerial and terrestrial Stonehenge, to be completed by winter 2013, provided new
125