Geophysical Survey in Archaeological Field Evaluation - HELM

Contents
Preface to the Second Edition . . . . . . . . . 2
Part I Standards for Geophysical Survey
1 Introduction . . . . . . . . . . . . . . . . . . . . . 3
2 Guidance . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1 Justification for survey . . . . . . . . . . . . . . 3
2.2 Fieldwork . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 Data treatment . . . . . . . . . . . . . . . . . . . . 4
2.4 Data interpretation . . . . . . . . . . . . . . . . 4
2.5 The survey report . . . . . . . . . . . . . . . . . 4
2.6 Dissemination . . . . . . . . . . . . . . . . . . . . . 5
2.7 Data archiving . . . . . . . . . . . . . . . . . . . . . 5
2.8 Competence of survey personnel . . . . 5
Part II Geophysical Survey and Planning
1 Archaeology and planning . . . . . . . . . . . 6
2 MoRPHE . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 Start-up and planning . . . . . . . . . . . . . . 6
2.2 Execution . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 Closure . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 Briefs and specifications . . . . . . . . . . . . 7
3.1 The brief . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 The specification . . . . . . . . . . . . . . . . . . . 8
4 The survey report . . . . . . . . . . . . . . . . 9
4.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2 Introduction . . . . . . . . . . . . . . . . . . . . . . 9
4.3 Methods . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . 9
4.6 Site location plan(s) . . . . . . . . . . . . . . . . 9
4.7 Data presentation –
plots and plans . . . . . . . . . . . . . . . . . . . 10
4.8 Plots of raw data . . . . . . . . . . . . . . . . . 10
4.9 Plots of processed data . . . . . . . . . . . . 10
4.10 Interpretative diagrams . . . . . . . . . . . 10
5 Dissemination . . . . . . . . . . . . . . . . . . . 10
5.1 Sources of information . . . . . . . . . . . . 10
5.2 Dissemination requirements . . . . . . . . 11
6 Archiving . . . . . . . . . . . . . . . . . . . . . . . 11
7 Legal considerations . . . . . . . . . . . . . . 11
7.1 Access . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.2 Metal detectors . . . . . . . . . . . . . . . . . . 12
7.3 Geophysical survey . . . . . . . . . . . . . . . 12
Part III Guide to Choice of Methods . . 13
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 13
2 Choice of geophysical survey . . . . . . . . 13
3 Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4 Urban (and brownfield) sites . . . . . . . . 14
5 Cemeteries . . . . . . . . . . . . . . . . . . . . . . . 15
6 Alluvium . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7 Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . 16
8 Road and pipeline corridors . . . . . . . . . 17
9 Wind farms . . . . . . . . . . . . . . . . . . . . . . . 17
10 Extremely large areas . . . . . . . . . . . . . . 18
Part IV
Practitioner’s Guide to Good Practice
1 Application of techniques . . . . . . . . . . 19
1.1 The survey grid . . . . . . . . . . . . . . . . . . . 19
1.2 Magnetometer survey . . . . . . . . . . . . . 20
1.3 Earth resistance
(resistivity) survey . . . . . . . . . . . . . . . . . 24
1.4 Ground penetrating radar . . . . . . . . . 28
1.5 Electromagnetic methods . . . . . . . . . . 34
1.6 Topsoil magnetic
susceptibility survey . . . . . . . . . . . . . . .36
1.7 Other geophysical methods . . . . . . . . 37
1.8 Metal detecting . . . . . . . . . . . . . . . . . . 40
1.9 Geochemical methods . . . . . . . . . . . . 40
1.10 Remote sensing . . . . . . . . . . . . . . . . . 41
2 Analysis of geophysical data . . . . . . . . 41
2.1 Data processing . . . . . . . . . . . . . . . . . . 41
2.2 Data display . . . . . . . . . . . . . . . . . . . . . 45
2.3 Data interpretation . . . . . . . . . . . . . . . 49
References . . . . . . . . . . . . . . . . . . . . . . . 50
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . 54
Appendix I Related standards,
codes and guidance . . . . . . . . . . . . . . . . 56
Appendix II Contacts . . . . . . . . . . . . . . . 57
Appendix III Useful websites . . . . . . . . . 58
Appendix IV List of consultees . . . . . . . 59
Contributors . . . . . . . . . . . . . . . . . . . . . 60
Acknowledgements . . . . . . . . . . . . . . . . 60
Part I
Standards for Geophysical Survey
1 Introduction
There is currently no formalised standard
for the conduct of geophysical survey in
archaeological field evaluation. For the purpose
of this guidance, however, it is expected that
such survey will, as far as is reasonably possible,
determine the nature of the detectable
archaeological resource within a specified area
using appropriate methods and practices 1 .
These will satisfy the stated aims of the
survey project. Members of the Institute
of Field Archaeologists (IFA) will, and other
practitioners should, comply with the Code
of conduct, Code of approved practice for
the regulation of contractual arrangements in
field archaeology, and other relevant by-laws
of that Institution 2 .
1 All relevant fieldwork must conform to the
Standard and Guidance set out by the Institute
of Field Archaeologists for archaeological
field evaluation.
(http://www.archaeologists.net/modules/
icontent/inPages/docs/codes/fldeval2001.pdf)
2 The IFA is the professional body for
archaeologists in the United Kingdom
(www.archaeologists.net). It exists to advance
the practice of archaeology and allied disciplines
by promoting professional standards and ethics
for conserving, managing, understanding and
promoting enjoyment of heritage. It has about
2500 members in the UK and abroad.
This basic requirement for geophysical survey
in archaeology is fairly straightforward, although
much will depend on the definition of what
is ‘reasonably possible’. To help address this,
we initially itemise below some more precise
requirements that must be achieved; followed
in Parts II–IV by more specific guidance on
best practice. Part II (Geophysical Survey and
Planning) and Part III (Guide to the Choice of
Methods) are aimed at those who commission
surveys; Part IV is a more in-depth description
and assessment of the main methodologies,
for those more concerned with these.
2 Guidance
2.1 Justification for survey
Prior to fieldwork, the geophysical survey
requirements must be integrated within
a written statement (the project design,
specification, written scheme of investigation, or
survey contract). This must include an explicit
justification for the choice of survey methodology,
while retaining some flexibility should this require
modification in the light of particular site
conditions at the time of fieldwork. The choice
of survey methodology will be appropriately
matched both with the archaeological and
logistical demands of the project.
3