Nondestructive investigation and recording have continued on field monuments. The earthwork henges at Knowlton, part of a striking concentration of Neolithic and Bronze Age ceremonial and mortuary monuments flanking the River Allen, have been the subject to topographical and geophysical survey as part of a wider programme of research into the Neolithic usage of the area. At Avebury, the remaining open area in the north-west quadrant of the Great Henge was the subject of resistivity survey after new features were noted on recent air photography by the Royal Commission on the Historical Monuments for England.
Although Stonehenge has been the subject of archaeological study for several centuries, until recently there was no detailed record of the carefully shaped faces of the individual stones. This has now been remedied by the provision of a complete photographic-based archive of every stone surface, together with a photogrammetry-derived and computer-generated Digital Elevation Model for each stone and group of stones. The surfaces of the stones can now be viewed under variable lighting from any angle on the basis of measurements taken at 2cm intervals across every face of every stone. This achievement marks the culmination of a rolling programme of survey and recording begun in 1989 as a result of which Stonehenge is now accurately described and tied into its immediate landscape. Initially intended as an archive record and a tool for conservation management, this work has additionally provided the database for the Virtual Reality model of the monument.
Built following the English Civil War, the Royal Citadel at Plymouth is another of England's premier landmarks: the north gate in particular is an outstanding example of 17th-century baroque military architecture. The elevations of its massive ramparts have now been recorded through a combination of photogrammetry and digital rectified photography as the first stage in a rolling programme of survey.
Two major items within the parallel programme of disseminating the results of earlier excavation projects were the receipt of reports on work at Halangy Down and Ludgershall. The remains of the prehistoric village on Halangy Down are among Scilly's best-known monuments, having been excavated by Dr Paul Ashbee between 1964 and 1977. An early (possibly late Neolithic or early Bronze Age) settlement has been engulfed by the sea, although up-slope its fields and 2 entrance graves still survive. A subsequent Iron Age settlement, with a second series of fields and enclosures, continued in use for almost a millennium until overwhelmed by blown sand some time around the 7th century AD. The royal castle at Ludgershall was excavated between 1964 and 1972 but for various reasons it was not possible to publish a report on the work at the time. A report by Peter Ellis has now been received setting out the evidence and relating it to the exceptionally rich medieval documentation. The castle was strongly defended by the standards of the late-11th-century and was an important stronghold during the civil war of the 12th-century: by the 13th century, however, it had become a hunting lodge, a role it retained until the 15th century.
