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AERIAL ARCHAEOLOGY RESEARCH GROUP

Annual Meeting, Aberdeen University 5-7 September 2000.

The following summaries were presented in four thematic sessions indicated in bold with the chair shown in brackets.



The use of "historic" air photographic sources (Rog Palmer).

RAF and Luftwaffe sources for Scotland.

Dave Easton
Royal Commission on the Ancient and Historical Monuments of Scotland,
John Sinclair House, 16 Bernard Terrace, Edinburgh, EH8 9NX.
E-mail: davide@rcahms.gov.uk

The National Monuments Record of Scotland (NMRS) now holds two sources of photographs from the Second World War. A batch of some 126 Luftwaffe photographs and copy negatives, which have now been available in the public area of the NMRS for some time, and a large batch of prints taken by RAF Photographic Reconnaissance Units. The RAF photographs were taken by units which, whilst under training, were based or flew from Wick, Dyce and Leuchars airfields. Many of the prints record World War II military sites in Scotland at the height of the war, between 1941 and 1943. The flights were primarily undertaken to train pilots both in vertical and oblique aerial photography; they may also have been used to train photo interpreters. Unlike the RAF photographs, the Luftwaffe vertical air images are target photographs, and they have been annotated by air photo interpreters.

The RAF wartime air photograph collection form part of the photographic archive that was transferred from the Scottish Office to the NMRS in 1993, and it is a particularly valuable source of information on Scotland in the immediate post-war period. Heavily used by the public, it has become one of the main records of the landscape from this period. The RAF wartime material there was part of what was known as the ‘restricted photographs’, which covered military establishments both wartime and post-war. Within the RAF wartime material is a collection of oblique images taken by what was known as No.1 CAM unit, for the specific purpose of examining and assessing camouflage schemes painted on industrial and military buildings. Totalling some 600 images, they provide a unique record of industrial and urban sites from that time. Little is known about this squadron, the aircraft used or those who comprised the personnel.

Examples of the images include many of the Scottish wartime airfields, often with aircraft visible in their dispersal bays, military camps, heavy anti-aircraft batteries and radar stations. In addition, many townscapes and landscapes can be seen on the sorties, especially where they form part of a ‘photographic run’, which has inevitably covered the area surrounding the target. Unfortunately, the negatives for all the RAF wartime collection was destroyed during the 1950s because of their unstable chemical composition, thus leaving the photographic prints as the only record of this work. RCAHMS is conserving the original prints to allow public access to this important collection. Catalogues of both collections have now been published; a third volume, selected from the post-war collection is in preparation.

It is clear that this collection of Luftwaffe and RAF images taken during World War II provides much useful information about defence sites in Scotland during this period. What is possibly less well known is that because they covered much of the surrounding area, they are also of value to those interested in the landscape studies. This is especially so in the case of the RAF material, which were photographed at low altitudes (for obvious reasons) and cover a wider geographical spread than the Luftwaffe flights. In addition the RAF images are of interest to the industrial archaeologist, as many of the structures photographed no longer exist. Whilst the Luftwaffe images have a certain cachet at present, it is the photographs taken whilst training RAF pilots to fly straight and level that are far more useful to those trying to understand not only defence works during the war, but also those interested in the landscape.

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RAF sortie WL10, 4 July 1942, frame no.2.40: vertical air photograph of the heavy anti-aircraft battery near Hardbreck, Orkney. Visible are the four gun-emplacements and accommodation camp. With north to the top, the gun-laying radar unit (GL-mat) can be seen immediately to the south of the battery. And at the extreme lower edge of the photograph the accommodation camp for another heavy anti-aircraft battery. Hardbreck was numbered M8 (M signifying mainland) by the War Office during the war and the anti-aircraft battery just out of frame was M9. Copyright: Crown Copyright: RCAHMS (RAF Collections).

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No.1 CAM oblique no.AF855, 9 May 1942. Oblique air photograph of Aberdeen. Visible are some of the shore defences along the sea front, including a pillbox and anti-glider trenches. Just visible are several small anti-tank blocks positioned in every gap in the sea wall. The docks are full of various inshore naval vessels and fishing boats. Notable is the abandoned fairground by the sea wall lower centre. Copyright: Crown Copyright: RCAHMS (RAF Collections).




Reconstructing Cornwall’s wartime landscape: the use of historic vertical air photography.

Andrew Young
Cornwall Archaeological Unit,
Kennall building, Station Rd, Truro. TRI 3AY,
Email cau@planning.cornwall.gov.uk

Vertical photos from the 1940’s are the most important source for the National Mapping Programme in Cornwall. More than 80% of our 3500 new sites are derived from these photographs. 1940’s photographs are particularly useful for the recording of World War 2 features, many of which were still in existence at the time of the photography.

The NMP is not just about plotting individual sites. It is a major source of information about the way in which the landscape has developed over time. Although the NMP has played a crucial role in recreating the wartime landscape, its impact has been dramatically enhanced by its working in conjunction with the Defence of Britain Project.

Historic vertical photographs, plus additional information from the DOB, have enabled us to recreate the complete defences of strategic towns such as Falmouth and Hayle, the anti-invasion defences of all the major beaches, and the defences around important military installations such as airfields. As Britain went more onto the offensive after 1941, we can trace the expansion of airfields and the construction of embarkation points for the D-Day invasion of 1944.

The real value of historic verticals in recreating this landscape is in the recording of ephemeral features. Aircraft obstruction pits, fake field boundaries laid out to disguise airfields, and tent encampments housing American D-Day troops are all visible on 1940’s photos and have been plotted. Air photography provides the only opportunity to record these short-lived features which form an integral part of the wartime landscape.




Lunchtime informal session.

Digital Image Processing, GIS, Digital Mapping, Visualisation and the Internet: Applying Information Technology to Coastal Zone Management.

David R. Green and Stephen D. King,
Centre for Marine and Coastal Zone Management,
Department of Geography, University of Aberdeen,
Elphinstone Road, Aberdeen, AB24 3UF, Scotland.
Email. d.r.green@abdn.ac.uk or s.d.king@abdn.ac.uk

Information Technology (IT) is increasingly offering a wide range of potential end-users a very powerful data handling 'toolbox' for processing geospatial data into information for numerous environmental applications. For example, in coastal zone management, where remotely sensed imagery (captured with traditional cameras, digital cameras, video, and scanners) can be input, stored, analysed, interpreted and delivered on-screen, integrated with other geospatial data within a GIS. In addition, maps can be delivered across the Internet, and visualised in a wide variety of different ways including using animations and 'fly-throughs'. Using powerful digital image processing software e.g. Erdas Imagine, PCI EasiPace and ER-Mapper it is now possible to enhance imagery to facilitate the extraction of information in the form of features and spatial patterns. Layers of information can then be integrated with other sources of environmental data within a GIS, providing a valuable source of information for spatial analyses, modelling and scenario generation. Both images and spatial data and information can now be delivered across the Internet to a wide range of end-users in new and very exciting ways that not only link disparate datasets in a single computer environment, but also deliver the information in a form that is not otherwise possible, offering new perspectives on the environment. 3D visualisations are providing new insights into environmental processes over both space and time, and helping more people to participate in environmental issues. New developments in image and map web servers are permitting rapid access to large image and map archives and databases. Such access provides greater opportunities for more people to make use of multiple datasets to aid in for example image interpretation and analysis. This short demonstration presented a brief overview of some of the work currently being carried out by the authors in the Centre for Marine and Coastal Zone Management (CMCZM) at the University of Aberdeen utilising a combination of geospatial technologies: including remotely sensed imagery (model aircraft and microlight platforms) from airborne, spaceborne and ground-based platforms (panoramic imagery), digital image processing (DIP), GIS, digital mapping, Global Positioning Systems (GPS), handheld computers, mobile phones (WAP technology), and image and map-based web servers. Examples drawn from the Solway Firth and the Fal Estuary in Cornwall in the context of integrated coastal zone management were used to illustrate the presentation.

 

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The role of air photography in site and landscape management (Mike Anderton).

The use of aerial photography in historic landscape characterisation in Wales.

Dave Thompson
Gwynedd Archaeological Trust, Craig Beuno, Ffordd y Garth,
Bangor, Gwynedd. LL57 2RT
E-mail: dthompson@heneb.co.uk

Over the past four years, the Welsh Archaeological Trusts have been carrying out a series of historic landscape characterisation exercises, funded by Cadw: Welsh Historic Monuments, to add detail to areas outlined in the Register of Landscapes of Outstanding Historic Interest in Wales (Cadw/CCW/ICOMOS, 1998).

At present there is no standard, accepted methodology for establishing the historical character of landscape, but recent work in Wales, using a standardised methodology agreed by Cadw, the Welsh Archaeological Trusts and the Countryside Council for Wales, has suggested that a practical approach based on considering the historical evidence as a series of themes might provide an answer. At a landscape level, what is significant in historical terms might include field boundary patterns (whether they are irregular or regular, their size, date etc.); settlement patterns (whether scattered or nucleated, date of origin etc.); the relict remains of earlier periods which are to be found in upland or marginal landscapes; the effect of 18th and 19th century estate improvements; the impact of industry, military installations, communication routes and so on.

Information is taken from a wide range of sources including primary and secondary archives, aerial photographs, old and modern maps, the sites and monuments record and primary fieldwork. One particularly useful source of data is recent vertical aerial photographs, and this is one of the two principal uses of aerial photography in landscape characterisation (the other is explained below). Using these data, discrete areas are then defined on a modern 1:25,000 map by visible consistent character which accords with evidence from one or more of these themes, backed up by supporting information on date, archaeological data etc. (all areas are unique, although some do form a recognisable 'type').

These areas are then assigned conservation priorities and broad management actions to try to retain their essential historic landscape character. The areas and priorities can then be fed into management initiatives such as the Countryside Council for Wales’s LANDMAP (Landscape Assessment and Decision-Making Process), which itself is beginning to feed into unitary authority schemes such as the new Unitary Development Plans, countryside strategies, AONB management plans and so on. It must be emphasised that this work is aimed principally at non-archaeologists: although it does have research implications, its main use is as a management tool. Characterisation identifies what is significant and distinctive in local areas, so that appropriate management strategies can be implemented by non-archaeologists which retain the essential character and integrity of the local landscape.

The principal aim and achievement of this work has been in getting across the idea that all landscape is historic (as well as natural), and there is much valuable historical and archaeological evidence in the pattern and detail of the countryside which we can use to help interpret and write the history of our landscapes. Here we come to the second principal use of aerial photography in characterisation. Good, oblique, colour aerial photographs of landscapes are very effective as conservation and education tools, as they allow archaeologists to tell stories (and thus sell our message) to people in straightforward and interesting ways. Everyone, it seems, reacts to their local landscape and wants to find out more about it, why it looks as it does, and what it looks like from a different perspective - the air.

Oblique photographs are frequently used in the presentation of the results of these projects. This is at several levels, from the formal reports to Cadw (which are laid out in sections with individual descriptions of each character area, alongside a map showing the extent of that an area and a photograph (usually aerial) which shows its principal characteristics), through leaflets and displays to web sites.

An example will serve to illustrate. The photograph shows the site of the medieval township of Morfa (now Morfa Nefyn) on the north coast of the Llyn peninsula. Its principal characteristics include a small, nucleated settlement (containing 18th and 19th century cottages, as well as modern development) set within an earlier enclosure (possible henge?), surrounded by an extensive area of strip fields (undoubtedly relict medieval open field strips fossilised below later cloddiau), which are divided by dog-legged lanes and tracks, again presumably relict medieval. Interestingly, this field pattern is restricted to the former parish of Nefyn (a medieval borough), and does not extend beyond. The area is bisected by the 1803 turnpike road (which runs in a straight line from top left to bottom right in the photograph), along which much of the 19th century ribbon settlement developed. On the management side, it was noted that the fields, being very small, were beginning to disintegrate and the cloddiau (earth banks) were beginning to be replaced with post and wire fences leading to loss of integrity and character. Now that the character and importance of this area has been highlighted, efforts can be made, where appropriate, within various rural initiatives (such as Tir Gofal, the all-Wales agri-environmental scheme) to conserve and manage this landscape.

While there will always be a need for management at the level of an individual archaeological site, there is an increasing need for archaeological and historical information at a landscape level, because it is at this level that the countryside of tomorrow is being shaped. Aerial photography therefore has a significant role to play in influencing the future.

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Blaenavon: mapping a nominated WHS with aerial photography and GIS.

Toby Driver and David Thomas
RCAHMW
Crown Buildings, Plas Crug, Aberystwyth, Ceredigion. SY23 1NJ.
E-mail: toby.driver@rcahmw.org.uk

The paper deals with the work the Royal Commission has been doing in support of the World Heritage Site Nomination for the Blaenavon Industrial Landscape in South East Wales. The area around Blaenavon is one of the finest examples of a landscape created by coal mining and ironmaking in the late 18th and early 19th centuries. The parallel development of these industries was one of the key forces of the world’s first industrial revolution, in which south Wales played a leading part. Many early industrial features survive in the landscape, including the core site of Blaenavon ironworks, dating from 1789, which is the most complete ironworks of its type and period remaining in the world. What makes Blaenavon so special is that these monuments still survive alongside limestone quarries, ironstone and coal mines, water-powered forges and intact transport systems. In short, Blaenavon is not just a series of industrial monuments but an integrated landscape within which key monuments of national, and international, importance are preserved.

During 1998 and 1999 the Welsh Royal Commission carried out two long flights over Blaenavon in support of the World Heritage bid. New photography was needed for our own archive, while photographs of specific views were required to illustrate the Nomination Document. These flights were by no means the first time the Royal Commission had over-flown Blaenavon. Since a flying programme started at the Welsh Royal Commission, in 1986, the recording of rapidly vanishing industrial landscapes across Wales, particularly in Glamorgan and Gwent, has been a key part of our remit. Since the early 1990s too, the aerial monitoring of over 600 Scheduled Ancient Monuments a year has been a core part of our flying programme, directly informing Cadw’s site management work.

The current targeted aerial reconnaissance, in support of the World Heritage bid, was geared towards obtaining aerial views which would set the key monuments in their landscape context, particularly wide-angle views to illustrate the shape and character of the landscape. The aerial photography also allowed non-specialists to appreciate the value and complexity of these palimpsest landscapes surviving within the nominated world heritage site. In the view of Hill Pits, picked out in low evening light, one can make out at least two phases of spoil tips resulting from the exploitation of coal seams, as well as features associated with redundant farmsteads.

During the recent photography of Blaenavon, it has been equally important to record these farmstead sites. Not only do they show the beginnings of settlement and farming in the Blaenavon valley, but they also belong to a class of monument, Deserted Rural Settlements, which are the focus of a great deal of new survey and protection in Wales, to which our aerial survey continues to respond.

The aerial views can tell only part of the story, and are of limited value without subsequent interpretation, mapping and integration into a wider programme of survey. David Thomas, in the second part of the presentation, describes the Blaenavon Landscape Project’s digital mapping work.

The Blaenavon Landscape Project was used as a pilot to explore the application of GIS within the Commission, with particular reference to landscape survey. Consequently, a wider range of sources was employed than would have been normal in an air photo mapping project, including geological maps, early cartography and historic photography. A series of GIS related techniques, including image manipulation, 3D visualisation and hot links to related imagery were also explored, enabling the creation of a detailed and accurate record of archaeological features across the 33 square kilometres of the World Heritage site. A number of previously unrecognised early industrial features pre-dating the ironworks were identified, as was as a wealth of information detailing the landscape changes that followed the foundation of the works. These landscape changes demonstrate clearly how a remote agricultural community developed into the complex industrial one which flourished throughout the nineteenth and into the twentieth century. The location of early industrial features that have now disappeared were also predicted, including a high railway viaduct constructed during the 1790s but buried underneath mine waste in the first half of the nineteenth. Maps from 1812, 1814 and 1821 were used to identify its position, which was tested in a recent edition of the Time Team television programme.

Three dimensional visualisation and links to related imagery, combined with a chronological sorting of the results of the air photo mapping, created a project that could convey the nature, extent, and significance of the archaeological features. This was used in a number of presentations to a wide range of audiences, including those involved in the World Heritage bid. It is hoped that future development of the information will lead to its integration into a management system for the World Heritage site. New ways of making the project available to a wider audience will also be explored, including the use of the Internet.

Figure 1: Hill Pits, Blaenavon, showing spoil tips from coal mining together with redundant agricultural features. (Crown Copyright RCAHMW).

Figure 2: Three dimensional modelling of Cwm Llanwenarth, showing the agricultural land in the valley bottom with limestone quarries and Garnddyrys forge above. (Crown Copyright RCAHMW).




Low-level (1800') medium format verticals for site condition reporting.

Kevin Jones
Department of Conservation, PO Box 10 420 Wellington, New Zealand.
E-mail: kljones@doc.govt.nz

Large-scale aerial photographs (approximately 1: 5,000 to 1: 10,000 scale on the negative) have a number of virtues for condition reporting. They are repeatable and objective and give sufficient detail to observe not only pattern but also the detail of condition in such matters as past repairs, sheep tracking or the existence and state of repair of fences. In addition a photo provides a ready base for annotation to act as the primary record of condition and to focus thinking on conservation intervention. Monitoring using photographs taken at intervals is also recommended.

Keywords: Archaeology, conservation planning, repair, restoration, Taranaki, Maori, prehistory, history, New Zealand.




Scottish Landscapes (Dave MacLeod).

Where is that sun - problems of flying in Aberdeenshire, Moray & Angus.

Moira Greig
Archaeology Service
Aberdeenshire Council, Woodhill House, Westburn Road, Aberdeen. AB16 5GB.
E-mail:mmgreig.ped@aberdeenshire.gov.uk

A light-hearted overview of the pros and cons of oblique air survey over Aberdeenshire, Moray, and Angus, which covers a diversity of landscapes from mountainous upland to coastal cliffs and plains. "Challenges" in the area include regular and serious mist, regular and serious military aircraft, and, of course, large areas with little or no control (a situation made worse when photographing in snow cover). The importance of GPS use is obvious in such landscapes. Much of the upland areas have received little archaeological survey, and winter flying regularly produces high numbers of new sites. A great diversity of monuments were illustrated including vitrified hill-forts, fishing villages, 18th century formal gardens, castles, mottes, crannogs, stone circles and upland MOLRS (medieval or later rural settlements)…and, of course, ridge and furrow. The images, as seen in Grampian’s Past, include excellent illustrations of the various techniques of capturing archaeological features under snow.

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Aboyne: Sinous strips of medieval ridge and furrow cultivation, surviving as earthworks, are revealed by a low light and hard frost (Copyright: Aberdeenshire Council Archaeology Service).

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Tap o’Noth: The second highest hillfort in Scotland, the site is a classic vitrified hillfort, an extensive burning of the site resulting in a fusing of the stone building material (Copyright: Aberdeenshire Council Archaeology Service).




The Impact of Aerial Photography Across the Lowlands of South-West Scotland.

Dave Cowley* and Kenny Brophy**
* Royal Commission on the Ancient and Historical Monuments of Scotland (RCAHMS), John Sinclair House,
16 Bernard Terrace, Edinburgh, EH8 9NX.
E-mail: davec@rcahms.gov.uk
** Department of Archaeology, The University of Glasgow, Glasgow, G12 8QQ. E-mail:
kbrophy@archaeology.arts.gla.ac.uk

The south-west of Scotland is not generally regarded as a happy hunting ground for cropmarks, but repeated flying by RCAHMS has yielded spectacular results that have had a dramatic impact on our view of the past and in particular of earlier prehistoric ritual monuments and later prehistoric settlements.

Aerial reconnaissance has served to confirm and extend distributions of certain classes of earlier prehistoric sites, such as henges and barrows. It has also revealed types of sites only visible as cropmarks, and our perception of the Neolithic has been revolutionised by the discovery of numerous large ceremonial sites, principally some 16 cursus monuments and the massive pit-defined circles at Dunragit. Excavations by Julian Thomas are now providing further detail on some of these sites and establishing their chronology (see www.arch.soton.ac.uk/Research/Dunragit/).

The impact of aerial photography on the distribution of later prehistoric settlements has been no less dramatic than on the pattern of earlier ceremonial monuments. While it has extended the scatter of small settlement earthworks known on the hills of the Anglo-Scottish Border throughout the lowlands of Galloway, it has also revealed the existence of timber-built settlements of a type previously unknown in any numbers west of the Annan. The distribution of Iron Age rectilinear settlements demonstrates the impact of aerial reconnaissance most clearly. These settlements are a familiar feature of the Border hills and have been recorded as cropmarks on the coastal plain in Northumberland in the east and eastern Dumfriesshire to the west. A single example in the west, near Wigtown, was for a long time anomalous, and until its excavation in the 1970s was regarded as of potentially Medieval date. Rispain was one of three earthwork settlements to which 56 further examples, recorded as cropmarks, can now be added. In the light of this explosion in the known distribution, the rectilinear settlements can now be seen as an element in the repertoire of later prehistoric settlement, rather than as peculiarities which excited curious interpretations.

The illustration depicts two subtly different rectilinear settlements on Cairn Connel Hill, near Stranraer. Both have a similar internal plan with houses ranged along the back of a yard, in a pattern repeated across the Borders. The relative dates of these enclosures is not known but the subtle differences between them may be a sign of settlement expansion, with the establishment of a new discrete unit. They may have been the improved farms of the day, reflecting the intensification of agriculture in the Iron Age from Northumberland to the Rhins in the west. The ‘sausage-shaped’ cropmark beside the unenclosed round-house may be a souterrain, a class of monument whose presence in the south-west of Scotland has only been revealed by cropmarking. What may be the ring-ditch of a small barrow lies adjacent and the elongated, E-W aligned, pits of a long-cist cemetery, probably of early Christian date, can be seen around the round-house and souterrain. The subrectangular cropmark may betray the location of a Grübenhaus, a form of building rare in the south-west, but increasingly emerging from the cropmark record.

The programme of aerial survey has seen an explosion in such information and, coupled with the results of excavation, there is a solid basis from which analysis can proceed. Excavation has a fundamental role to play, providing evidence for dating and use, but it is an expensive and slow process, which can only hope to examine a minute percentage of known monuments. Consequently, analysis of the mass of material which has been recorded already is vital if excavations and other work are to be directed towards the monuments that may illuminate wider patterns.

A full version of this paper will appear in the Transactions of the Dumfriesshire and Galloway Natural History and Antiquarian Society, to be published in summer 2001.

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Cairn Connel Hill, Stranraer: enclosed settlement appearing as cropmarks

(Crown Copyright:RCAHMS).




Macro- and Micro-Land Division in the Later Prehistoric Period: Aerial Survey, Pit-Alignments and GIS in South-East Scotland.

Marilyn Brown Royal Commission on the Ancient and Historical Monuments of Scotland, John Sinclair House, 16 Bernard Terrace, Edinburgh, EH8 9NX, Scotland E-mail: Marilynb@rcahms.gov.uk

The Royal Commission on the Ancient and Historical Monuments of Scotland has been carrying out consistent aerial reconnaissance in south-east Scotland for over twenty years. While the presence of pitted features had been recorded in earlier years, it was in 1978 that an association was noted between pit-alignments and settlements appearing in cropmark and earthwork form and attributed conventionally to the Iron Age. It could be suggested that these land divisions related to the use of the land in the area immediately around the settlement. In the 1980s there was a gradual increase in the information recovered from cropmark aerial reconnaissance, building up the database and transcribing information at 1:10,000 scale onto paper maps, reinforcing associations and adding to its complexity, but also producing a considerable number of examples which could not be obviously associated with any one settlement.

There are two main forms of linear boundary in the cropmark record, linear ditches and pit-alignments or interrupted ditches. They are paralleled as upstanding monuments by linear earthworks, which usually appear as a bank and a slight, presumably quarry, ditch and, in a very few examples, as a series of small, regular depressions, accompanied by a low bank, which match the pit-alignments. The pits are usually quite small, between 2m and 3m in diameter and often poorly defined. Pit- alignment is a convenient morphological term, which may be applied to monuments of different periods and cultures. The most usual alternative association for this phenomenon is with Neolithic ceremonial monuments, such as the pitted curvilinear enclosure excavated at Meldon Bridge on the south-western edge of the study area, and most pit-alignments in south-west Scotland and probably northern Scotland share this cultural association rather than the later prehistoric one considered here. Examinations of the distribution patterns in GIS show a clear concentration in south-east Scotland, and in certain areas within it. Because of their distinctive form, pit-alignments are easier to isolate in the archaeological record than linear cropmarks, which are usually selected by the aerial surveyor as examples which do not fit the pattern of linear features belonging to the post-medieval period such drains, pipe trenches, ploughed-out field boundaries or ditches around former plantations among other phenomena, so that there is a greater element of subjectivity in their recording.

With the 1990s came a survey break-through, allowing the relationship between pit-alignments and linear cropmarks to be clearly established, and, with the advent of GIS in the Royal Commission, came the ability to view these very small individual features both in isolation and as part of larger grouping, which can, in the most extreme example, be seen to run for at least eight km. The digitised transcription and rectification of pit-alignments, linear cropmarks, the settlements with which they may be associated and earlier monuments, which may have been utilised in the laying out of boundaries, and the incorporation of information into the GIS is time-consuming work, of which perhaps has been completed so far. Examples were recorded running uphill into the currently uncultivated moorland and even to the cliff edge above the North Sea, implying a completeness of control of the land, that required detailed physical boundaries defining small areas, which might be compared in scale to the modern field pattern, the product of enclosure between the late seventeenth century and the early nineteenth century, and perhaps allowing movement between certain areas with cattle excluded from crops or grazing. The discovery of a surviving pit-alignment and associated low linear banks, only visible from the air under extreme light and vegetation conditions, situated at a height of about 350m, would indicate that, while other examples may survive in upstanding form, they will only be identified with difficulty. The only excavation in the study area of part of a pit-alignment, one pit, yielded no dating evidence, but excavations of comparable features in England might indicate a date in the late prehistoric period. The results of a series of recent pollen analyses across southern Scotland and northern England would suggest that about 300BC, there was a very considerable expansion of cultivation across the area, and this dating would not conflict with the field evidence. The paper concerns itself with the evidence for Scotland, but, in conclusion, would make a plea for GIS, unrestricted by boundaries; the evidence for similar features continues across the Border at least as far as the River Till, some 25km into Northumberland, and two pit-alignments, whose northern end lies in Scotland can be seen continuing into England. The evidence for an ordered and complex system of land division in south-east Scotland is considerable, and perhaps raises questions about the organisation of the inhabitants of the area in the second century BC, the tribe named by the geographer Ptolomy as the Votadini.




Recent work and current affairs.

Continental Affairs.

Otto Braasch

An account of developments on the continent and the good year for the production of cropmark in some areas, including Austria and Hungary. Otto also suggested the idea of a "task-force" which could be set up in order to react to such conditions, ideally involving a sum of money set aside which could be targeted to areas that prove to be most productive.

Thinking and doing aerial photography in some prehistoric landscapes.

Dr Kenneth Brophy
Department of Archaeology, The University of Glasgow, Glasgow, G12 8QQ. E-mail: kbrophy@archaeology.arts.gla.ac.uk

This paper attempted to continue the debate initiated at the AARG conference in Bournemouth 1999 concerning the potential application of post-processualism in aerial photography. Rather than concern itself necessarily with the idea of power and knowledge, I wanted to instead think about the areas of aerial photography that we take for granted. The main theme of the paper then is the role of subjective input into a discipline that is essentially viewed as scientific, rigorous and objective. This attitude is typified by the military metaphors that surround the activity and the high-tech planes and cameras involved. I contrasted this with the random nature of aerial photography, a process as much guided by intuition and luck as by careful planning and methodological rigour. The paper also looked at interpretation in involved at every stage of the flight and post-reconnaissance, and argued that what we bring to the process inevitably shapes the results of our aerial surveys. This is not a weak-point, but rather a strength, recognised by most practitioners of aerial photography. An amended and extended version of this paper appears in this addition of AARGnews.




Landscapes and sources (Kenny Brophy).

Prehistoric and Romano-British landscapes on the Lambourn Downs - a typical southern chalk downland?

Helen Winton
English Heritage, Aerial Survey, National Monumnets Record Centre, Kemble Dive,
Swindon. SN2 2GZ.

The Lambourn Downs Mapping Project is part of English Heritage's, National Mapping Programme which aims to map all archaeology visible on aerial photographs for the whole of England. The findings of the survey emphasis that there is no such thing as a typical archaeological landscape on the chalk downland of Wessex. The survey recorded the "usual" Neolithic long barrows and numerous Bronze Age round barrows but found nothing comparable to the Bronze Age settlements and enclosures on the Marlborough Downs, Salisbury Plain Training Area (SPTA) and Danebury environs. Whereas elsewhere on the chalk downland of southern England, the large enclosures and hillforts often seem to form part of an integrated landscape with large linear boundaries and "celtic field systems", on the Lambourn Downs the "celtic" fields were Romano-British and the hillforts and linear boundaries seem to be mutually exclusive. The survey recorded a complex sequence of large and small-scale possible Late Bronze Age/Eary Iron Age land division which may or may not have been contemporary with a cluster of Iron Age Banjo enclosures. The majority of the upper part of the Downs has been blanketed with the Romano-British fields systems and associated settlements and it is only as these are ploughed level that the pre-Roman landscape begins to emerge, as cropmarks, underneath.




The Stour River Valley, Essex: DTMs and aerial photography.

Davy Strachan
Perth and Kinross Council, Museum and Art Gallery, 78 George Street, Perth, PH1 5LB.
E-mail: DLStrachan@pkc.gov.uk

A summary of the methodology and findings of work carried out by Essex County Council and funded by English Heritage, on the Stour river valley. The project involved composite image rectification of 334 sites ranging from single ring-ditches to complex, multi-phased sites. The river valley contains a concentration of prehistoric monuments including ring-ditches, dual concentric ring-ditches, long mortuary enclosures/long barrows, and cursus monuments. The cropmark plots were draped over a DTM based on 5m contour information, allowing the sites to be viewed in relation to the river and the surrounding terrain. A simple morphology of sites was devised to enable cumulative view-shed analysis of selected site-types to be carried out. These intervisibility studies tended to re-enforce field-observations that many of the larger complexes were positioned on the river where visibility was restricted by the surrounding terrain, creating a natural amphitheatre-effect. Details of the project can be found in AARGnews 20 and on the AARG website. A further report on the work is planned for the forthcoming AARGnews.




Aerofilms & UK Perspectives Mapping Britain through the years.

Stuart Simmons,
Simmons Geomatics Group Limited, 5 West street, Somerset, BS26 1AA.
E-mail: stuart@simmonsmap.com

Established in 1919 by Francis Wills, an air photographer with the Royal Flying Corps, Aerofilms has always been at the forefront of aerial photography in the UK, and now boast an archive of over 2.25 million images, including an international collection from the 1950s and 60s. UK Perspectives http://www.ukperspectives.com is a collaboration between Simmons Aerofilms (http://www.aerofilms.com/) and NRSC (http://www.nrsc.co.uk/), and has recently produced the Millennium Aerial Photographic Survey (MAPS) which has produced colour vertical photography at a scale of 1:10,000, which is scanned and geo-referenced for GIS use. The presentation included examples of how vertical sources and historical imagery can be combined using ERMapper software to study changing environments.

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Western Riverside, Bath, 1946: a classic brown field site that is without doubt contaminated as gas works and other heavy industry can be identified from the imagery revealing Bath's industrial heritage. The Council intends to finance the remediation through a careful balance of commercial, leisure and residential facilities that contribute to a vibrant area in the centre of Bath. Planning proposals include the relocation of Bath Rugby Club (copyright Aerofilms Ltd).

 

 

 

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Radstock: another brown field site, currently described as 'industrial derelict'. It could also be regarded as a conservation area due to the rich diversity of species living within the site. Historical and contemporary Aerial Photography, in digital form, can display the true nature of the site in question more effectively than a traditional vector map can. Therefore any development initiative taken has to consider both the economic need for redevelopment as well as the need for conservation (copyright Aerofilms Ltd).




The "digital revolution" and remote sensing (Michael Doneus).

The Trials and Tribulations of installing a Vertical Camera.

Anthony Crawshaw,
Conservation Laboratory,
15 Kings Staith, York Archaeological Trust, YORK, YO1 9SN Galmanhoe Lane, Marygate,
YORK. YO30 7DZ

My interest in installing a vertical camera in the Cessna 172, which is normally used by the Northern Flight of English Heritage, was sparked by the engineers finding an oblong opening in the floor of the aircraft. This hole, together with two suitable holes in the outer skin, has enabled us to install a medium format camera with TV guidance system. Alternative camera configurations are a 35mm. camera plus the TV camera or two 35 mm. cameras. The cameras are contained within an aluminium box that is sunk flush with the floor of the aircraft. The cameras are adjustable for drift, whilst airborne, and tilt when on the ground. The TV monitor is used to judge drift corrections, by turning the camera so that objects move straight down the screen.

Two test flights have taken place to date, one using a Vinten F95 camera and the second a Rollei 6008. The Vinten photography suffered from unsharp edges and corners of the photographs. This problem is still being investigated. By contrast, the Rollei prints were satisfactory, suggesting that the overall concept is workable. Two groups of prints, one from each run, have been rectified using Aerial 4.2, which returns the position of the aircraft as one result of the calculations. This position check has enabled us to confirm that the photographs are within five degrees of the vertical.

The Garmin GPS system is used to keep the aircraft on the required flight-line and tests have shown that it is possible to keep within one hundred metres of the flight-line. To date the work has cost œ1175, with an estimated cost to completion of another œ300. This cost excludes the considerable amount of time that the author has spent on the project.

I am grateful to the flying team at English Heritage for their patience with this project; also to Dave Sympson and John Cossins for their work on the mechanical and electrical components, respectively.




Digital airborne Remote Sensing: the Principals of LIDAR and CASI.

Nick Holden (Environment Agency)
Environmental Monitoring and Surveillance
National Centre for Environmental Data and Surveillance

LIDAR, LIght Direction And Ranging, is based on scanning a pulsing laser over the ground from an aircraft. By monitoring the direction of the incoming reflected pulse, and the time of flight of that pulse, the position of each hit on the ground in x, y and z can be determined. This data will in the first instance be in the WGS84 co-ordinate system. It can then be transformed into a total co-ordinate/grid system as required. The data has a high relative accuracy (10-15cm); although absolute accuracy will depend upon the datum to which you are working. Once a series of points has been computed, an elevation model (DEM) can be constructed. The Environment Agency first create a 2-metre grid, and for ease of handling, cut the data into 2km x 2km tiles. The grid is populated with the data, allowing some cells empty to be filled by a process of interpolation. Once this stage has been reached the process of data display and interpretation can begin. The data can be used to compute contours; colour code cells for height; strip data of vegetation and man-made features; build digital features into data; aspect shade from any angle; view from any angle; produce fly-through visuals; and overlay with other GIS compatible data. The LIDAR in its basic form will measure only position and height. The data chain is totally digital; the outputs are designed for visual interpretation in any standard GIS package. Any archaeological feature that causes a variation in surface elevation can be monitored. The system has no subsurface capabilities. It is able to collect data day or night at the rate of 30-40 sq. km/hr, thus allowing sites and features to be viewed in context within their surroundings. It is widely used for flood plain mapping, coastal zone management, soil erosion and diffuse pollution studies, recording open-cast mines and quarries, landfill sites, water resources and for near shore bathymetry.

CASI, Compact Airborne Spectrographic Imager, can be used for land use studies; vegetation classifications; vegetation stress; inter-tidal vegetation monitoring; effluent and riverine dispersion plumes; and dye tracing studies.

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Hambledon Hill, Dorset: LIDAR data showing the hillfort on the N spur with the internal long barrow and a probable neolithic ditch to the north. The image also shows the neolithic causewayed enclosure at the bottom right part of the image, containing quarrying recorded in 1924. LIDAR data allows the viewer to alter the angle and direction of the light source, allowing earthwork features to be viewed under the best lighting conditions (Data copyright The Environment Agency).




An assessment of LIDAR for archaeological use.

David Motkin, formerly with the Isle of Wight Council Archaeology Service.
Sunnymeade, Moor Lane, Brighstone, Newport, Isle of Wight. PO30 4DL.
E-Mail: motkin@onetel.net.uk

A rapid assessment of LIDAR data was carried out to determine its potential in archaeological work. Seventy-one 1km square data tiles covering the flood plain and lower slopes of the eastern Yar valley, Isle of Wight, were kindly provided by the Environment Agency. The data had been captured in mid-March 1998 when crop heights were minimal and many trees were leafless and was in the form of xyz ASCII files referenced to the British National Grid. It was loaded directly into the Vertical Mapper extension of MapInfo, with heights on a 2m grid. A 3D view of the data coloured according to height was obtained. The view could be vertical or oblique, from any direction or elevation. The position of a simulated "sun" was also infinitely variable. The resulting image was complete with simulated shadows, but the detail visible was due only to variations in height and not to the reflectivity of the subject. It was immediately apparent that the high resolution DTM was far superior to any other similar data and aided interpretation of the landform, allowing the locations of settlements and harbours to be postulated and questions to be posed. In some areas previously unrecorded ridge and furrow seemed to be present, but comparison with summer time photography showed that at least some of this corresponded with spray lines in wheat. Although it was probably not ridge and furrow, such would surely have been recorded had it been present. In known areas of shallow earthworks, manipulation of the "sun" position revealed features not previously seen. On arable land in the west of the sample area two large earthwork enclosures with banks only about 15cm high were observed. One of these is crossed by hedged boundaries including a parish boundary of probable Saxon origin. Although neither enclosure is visible on air photographs they are probably genuine. Site visits will be made when the crops have been removed. It was concluded that LIDAR has considerable potential in archaeology, but further study in this and other sample areas is required.

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LIDAR image showing possible earthwork enclosure at Mersley Farm, Brading, Isle of Wight (Data copyright The Environment Agency).




Satellite imagery: review and preview.

Martin J F Fowler
60 Harrow Down, Badger Farm, Winchester, Hants. SO22 4LZ
Email: mjff@compuserve.com WWW:
http://ourworld.compuserve.com/homepages/mjff/

Over the past 25 years, both the quality and availability of imagery acquired by remote sensing satellites in Low Earth Orbit has improved to the point where satellite imagery can now be considered to have a proven utility in archaeological prospection (see Fowler 2000). Although low resolution multispectral imagery from the LANDSAT Thematic Mapper (30m spatial resolution) is incapable of detecting all but the largest of archaeological features, it has been shown to have value in prospecting for areas of high archaeological potential through the use of image processing and modelling techniques (e.g., Cox, 1982). Similarly, medium resolution imagery such as SPOT Panchromatic (10m resolution) and declassified US CORONA imagery (effectively 5-10m resolution) can detect some of the larger archaeological features (e.g., Kennedy, 1998), but are of greater use in the preparation of base maps for regions for which accurate mapping may not be available. High resolution KVR-1000 (circa 2m resolution) and IKONOS (1m resolution) images are comparable to conventional medium-scale aerial photographs and are capable of detecting both standing and plough-levelled archaeological features (e.g. Fowler, 1996).

Currently, the archaeological utility of satellite imagery is limited by its relatively low spatial resolution when compared with the very high resolution of conventional aerial photography. This utility is further constrained by the relatively high cost of satellite products and orbital constraints that result in the collection of single pass images that are acquired at a specific time of day from a (largely) vertical perspective. However, these limitations can be offset by the 'Open Skies' nature of the orbital perspective that allows imagery to be collected over areas that are otherwise prohibited or impractical to aircraft (e.g., airspace reservations, political restrictions, inhospitable areas etc.). Furthermore, the large areas that covered by individual images (e.g. up to several hundred square kilometres for a single IKONOS image) can make this a cost-effective means of surveying a large area. As the spatial resolution of commercial imagery continues to improve (0.5m imagery appears to be on the horizon), costs fall, new products - such as high resolution multispectral and hyperspectral imagery - become available and distribution over the Internet develops, satellite products can be expected take their place as just another routine source of imagery in the aerial archaeologist's toolkit.

Cox, C. 1992. Satellite imagery, aerial photography and wetland archaeology. World Archaeology 24: 249-267.

Fowler, M. J. F. 1996. High resolution satellite imagery in archaeological application: a Russian satellite photograph of the Stonehenge region. Antiquity 70: 667-671.

Fowler, M. J. F. 2000. In search of history. Imaging Notes 15(6): 18-21. (Available on-line at http://www.imagingnotes.com/).

Kennedy, D. 1998. Declassified satellite photographs and archaeology in the Middle East: case studies from Turkey. Antiquity 72: 553-561.

One-metre resolution IKONOS image of the remains of CALLEVA ATREBATVM acquired on 17 February 2000. The upstanding walls of the Roman town can be readily seen in relief and, within the walls, some indication of the former street pattern together with the ongoing excavation of Insula 9 can be seen. Towards the top of the image, the characteristic outline of an itinerant Chinook helicopter is also apparent. Image supplied by Space Imaging © 2000 (http://www.spaceimaging.com). Reproduced with permission.

 




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