1. Geophysical Survey in the Archaeological Record:
The Archaeological Investigations Project
Bronwen Russell & Timothy Darvill
School of Conservation Sciences, Bournemouth University
Figure 5. Percentage of organization types conducting geophysical fieldwork in England
Figure 1. Number of planning applications received in England (figures from the Office of the Deputy Prime Minister) against the number of recorded planning related geophysical surveys undertaken
Far more local government and commercial units can now offer geophysical survey in their repertoire of evaluation techniques. The number of specialist geoprospection companies have grown in this climate and utilise a variety of instruments and techniques (figure 3) to aid in site investigation. Apart from the initial outlay it then becomes a very cost-effective way of also involving people in active archaeological research. The Council for Independent Archaeology have been developed a low cost resistivity meter and at least 25 units are currently in use by CIA members. The more affordable instrumentation and ease of use to the surveyor means that many more commercial archaeological units possess their own equipment.
This all means that an increasing number of geophysical surveys have been undertaken by a greater number of organizations year on year over the past decade (figure 5), and that a wealth of information is becoming available. AIP aims to record these events and map the trends which data analysis reveals.
With the advent of PPG16 (Planning Policy Guidance note 16) in 1990 archaeology in England has developed within a doctrinal climate centred around ‘preservation in-situ’. This has seen the rise of geophysical techniques as a rapid evaluation tool in planning-led archaeology (figure 1). This non-intrusive survey can greatly enhance the known archaeology of a site and its surrounding environs. In the case of evaluations it can be an invaluable way of locating trenches to target the archaeology. The variety of methods and availability instrument types means that the most appropriate method can be chosen for a project and by combining a number of methods a very detailed picture of the site can often be built up. Personal and public research projects also utilize geophysical survey techniques providing an essential research tool with quickly accessible results that can be used to illustrate the need for further work and develop future strategies. (see figure 2).
Figure 6. Comparison of the two main geophysical survey types used for field investigation recorded in England
Figure 2. Proportion of planning-related to research-related (non-planning) geophysical investigations recorded in England
AIP has always recorded geophysical surveys which form part of a broader evaluation consisting of a number of archaeological techniques, specialist geophysical surveys were recorded on the English Heritage Geophysical Survey Database. The GSD contains details of all AML geophysical surveys dating back to 1972, as well as a large number of other surveys carried out by other organisations and individuals, either registered as a requirement of permission for surveys to be conducted on a scheduled ancient monument, under section 42 of the Ancient Monuments Act, or sent in voluntarily to be included in the database.
The proliferation of geophysical surveys during the 1990s (figure 4) meant, however, that a more comprehensive approach was needed for tracking down and recording the nature, extent and distribution of geophysical surveys of all kinds. Thus data collection 2001 onwards for events undertaken in England now includes all geophysical survey work. It is hoped that this might then be used to support and enhance already existing data sets.
Initial analysis has provided some interesting results, such as the increasing dominance of magnetometry as the primary survey technique and the dramatic increase in the use of GPR in archaeological investigation. Due to the shift in emphasis in data collection future analysis will be more comprehensive and therefore more easily comparable on a national scale.
The Archaeological Investigations Project, funded by English Heritage seeks to record and provide a gazetteer of all archaeological investigations undertaken in England, year by year. It provides listings of archaeological interventions for each county and unitary authority in England and is the only systematically researched up to date record of its kind in England. The project researchers visit all county councils, commercial units and universities that undertake original fieldwork, while other workers are contacted by postal surveys. In addition to this AIP has recently published Archaeology after PPG16: archaeological investigations in England (2002). An analysis of the changing character and distribution of archaeological work in England since the introduction of PPG16.
The development and availability of affordable, user-friendly equipment and data processing packages means that many active local archaeological societies can afford at least basic resistivity equipment. This provides a useful non-invasive research tool which societies can employ to broaden their knowledge of archaeological sites and potentially contribute enormously to the enhancement of the local SMR/HER (Sites and Monuments Record/Heritage Environment Record).
Figure 4. Distribution map of recorded geophysical investigations in England
(where year and grid reference recorded)
Figure 7. Number of archaeological contracting units viewed against specialist geoprospection units conducting geophysical surveys in England
Figure 3. Percentage of recorded archaeological geophysical investigations in England by survey method
References:
Council for Independent Archaeology -
Darvill, T, and Russell, B, Archaeology after PPG16: archaeological investigations in England (Bournemouth University School of Conservation Sciences Research Report 10). Bournemouth and London. Bournemouth University in Association with English Heritage
English Heritage Geophysical Survey Database -
Geoscan Research -
Schmidt, A, 2002.Geophysical Data in Archaeology: A Guide to Good Practice. Oxford. AHDS, Oxbow Books.