Archaeology: An Introduction - 4th Edition 2002
The Online Companion: updated November 2007


CHAPTER 2 : Discovery and Investigation

>> CHAPTER OVERVIEW

2.1. SITES OR LANDSCAPES?

2.2. FIELD ARCHAEOLOGY

2.3. REMOTE SENSING

2.4. GEOGRAPHICAL INFORMATION SYSTEMS (GIS)

2.5. LANDSCAPE ARCHAEOLOGY

 

 


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2.1. SITES OR LANDSCAPES?

The expansion of large survey projects raised interesting problems about recording and classification which directed attention back to the question of defining a site. Few archaeologists would find any difficulty in recording artefacts or building materials found on the surface of the ground, or recognising and classifying physical features such as a stone wall or mound. But what combination of surface finds and surviving structures constitutes a site?

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2.2. FIELD ARCHAEOLOGY

2.2.1. Field Survey

2.2.2. Fieldwalking (and shovel testing)

2.2.3. Recording and topographic/earthwork surveying

2.2.4. Sites and Monuments Records

2.2.5. Underwater survey

 

2.2. FIELD ARCHAEOLOGY

Discovery is pointless without recording, but observers (ancient or modern) only record what they see, and what they see is determined by what they consider to be significant. Bias is inescapable, but may be reduced by modern archaeologists if they explain their ideas and research strategies explicitly, rather than treating fieldwork as an objective recording exercise.

2.2.1. Field Survey

Much fieldwork now takes place in the context of field survey - a comprehensive study of an area selected either because it is threatened with damage by development or agriculture or because it has the potential to answer questions generated by wider archaeological research.

2.2.2. Fieldwalking and shovel testing

Fieldwalking is the simplest procedure employed in fieldwork, and it provides many opportunities for amateurs and beginners to get involved. Although it may include the recognition of sites through minor fluctuations in the form or character of the ground in areas that have had little investigation in the past, the main purpose of fieldwalking is normally the collecting of artefacts from the surface of ploughed fields.

2.2.3. Recording and topographic/earthwork surveying

Ground-level photography remains important for documenting sites, and can place them into a local context as well as including people engaged in fieldwork to illustrate methodology.

2.2.4. Sites and Monuments Records / Historic Environment Records

Ideally, a database of sites, with plans, photographs and sources of further information, should serve a number of different purposes. These may include further research by individuals who were not involved in collecting the data, such as academic archaeologists or planning officers considering the impact of development proposals.

2.2.5. Underwater survey

Fieldwork under water is not unlike that on land, for it relies both on broad-scanning methods for identifying wrecks or other underwater structures, and on detailed visual inspection of smaller areas or individual locations by divers.

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2.3. REMOTE SENSING

2.3.1. Airborne prospection

:: Aerial photography

:: Multispectral and thermal prospecting

:: Photogrammetry

:: Interpretation of aerial images

2.3.2. Geophysical and geochemical surveying

:: Resistivity surveying

:: Magnetic surveying

:: Metal detectors

:: Ground penetrating radar (GPR)

:: Seismic prospecting and geochemical examination of soil

:: Underwater location devices

 

2.3. REMOTE SENSING

Remote sensing devices do make contact with the ground, but are still 'remote' from the buried archaeological features that they are designed to detect.

2.3.1. Airborne prospection

Optical aerial photography has undoubtedly made the greatest single contribution to archaeological fieldwork and recording. Besides giving attractive bird's-eye views of surviving sites, aerial photography is overwhelmingly important in bringing to light buried sites visible through discolorations in the overlying soil or vegetation .

----- Aerial photography

Aerial photography provides a useful supplement to observations made during fieldwork on visible sites with traces of earthworks or walls surviving above ground.

·         Introduction to Aerial Archaeology '...aerial archaeology is more than just taking photographs, although this was and sometimes is still considered to be its main subject. In fact, it goes far beyond the mere acquisition of data, and you even don´t need photographs to perform aerial archaeology: you can use also satellite images, thermal images or airborne radar images. To perform aerial archaeology means above all, to make archaeological use of this kind of remotely sensed information.' (Aerial Archive, Institute for Prehistory and Protohistory of the University of Vienna)

·         Aerial Archaeology Research Group (AARG) "...provides a forum for the exchange of ideas and information for all those actively involved in aerial photography, photo interpretation, field archaeology and landscape history. This also includes the use of aerial photography in defining preservation policies for archaeological sites and landscapes."

·         Archiving Aerial Photography and Remote Sensing Data - A Guide to Good Practice (Arts and Humanities Data Service). See in particular Section 2 (Aerial Photography, Remote Sensing, and Archaeology): 'This section presents a brief overview of the history and role of aerial photography and remote sensing in archaeology. It discusses the principal methods employed and, briefly, the data formats output. The section ends with a 'suggested reading' list pointing the reader to key texts.'

·         Cranborne Chase Bournemouth University: details of geophysical surveys and excavations, related to aerial and ground-level photographs of the sites

·         THE PAST REVEALED 'In 1928, a pilot flying over Caistor noticed a regular grid pattern of pale parched corn in the green barley fields inside and around the Roman town.' The photograph is accompanied by photographs of the excavation of stone structures, and forms part of A virtual tour of Caistor Roman Town, Norfolk. (John Peterson, University of East Anglia, Norwich, UK)

·         Baker Aerial Archaeology Introductory information and explanations, primarily from Southwestern U.S.A.

·         Aerial-Cam Commercial company offering low-level aerial photography from a telescopic mast extending up to 22 metres – no aeroplane required! Beautiful sample photographs of sites and buildings on this site.

----- Multispectral and thermal prospecting

From the 1970s airborne prospecting has expanded to include devices that record a wider range of wavelengths, including multispectral imaging sensors, thermal imaging radiometers and imaging radar. All of these collect data in digital form that is eminently suitable for processing by computer to produce the best results.

----- Laser scanning

This is a new technique for surveying surface remains from the air or from the ground. It can also be used to record standing buildings.

----- Photogrammetry

Conversion of optical photographic images into digital formats allows them to be used more easily with other data (for example from surveys and geophysical instruments) and incorporated into GIS.

----- Interpretation of aerial images

It is not always easy to distinguish between archaeological features and natural geological phenomena; a thorough knowledge of archaeology is required for any attempt to classify and date sites according to their form.

 

2.3.2. Geophysical and geochemical surveying

The use of geophysical prospecting devices is an efficient method of exploring invisible aspects of the buried site and relating them to a measured survey. As with aerial photography, the main purpose of geophysical instruments is to distinguish anomalies, hopefully of human origin, from the natural subsoil.

----- Resistivity surveying

When an electric current is passed through the ground between electrodes, the resistance to its flow may be measured. A current will pass relatively easily through damp soil, but drier compact material such as a buried wall or a cobbled road surface creates higher resistance.

----- Magnetic surveying

Magnetometers detect deviations from the general background of the subsoil, indicated by variations in its magnetic field. Several aspects of past human occupation cause suitable anomalies.

 

----- Metal Detectors

Metal detectors are not only popular with members the public who regard their use as an innocent hobby, but also with professional treasure-hunters who plunder sites for profit. Most types penetrate the soil only to a very limited extent, but they have been used by archaeologists to locate dispersed metal artefacts.

----- Ground penetrating radar (GPR)

Electronic signals are transmitted into the soil, and bounce back to a receiver. The signals are altered by the density and position of whatever they encounter underground, and the patterns received from the ground are plotted diagrammatically.

----- Seismic prospecting and geochemical examination of soil

Acoustic or seismic investigation is very common in geological survey and, in the form of sonar, used under water for archaeological purposes, but it has not been utilised extensively for archaeology on land.

----- Underwater location devices

Sonar scanning works in the same way as radar, but sonic (rather than electronic) signals are transmitted and received. Side-scan sonar can cover large areas because the signals are transmitted sideways to detect irregularities on the surface of the seabed.

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2.4. GEOGRAPHICAL INFORMATION SYSTEMS (GIS)

Computers that combine large data-storage capacity with fast mathematical processors and high-quality graphic display were typified in the 1990s by Sun workstations, but by the twenty-first century such features had become readily available on desktop PCs. Likewise, GIS software became less complex and more user-friendly over the same period.

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2.5. LANDSCAPE ARCHAEOLOGY

The term retrogressive analysis is sometimes employed to describe how landscape archaeologists work back from modern features to the fragmentary remains of earlier landscapes.

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