Geophysical Survey in Archaeological Field Evaluation - HELM

2
Preface to the Second Edition
These guidelines are intended to help
archaeologists, particularly curators, consultants
and project managers, to better understand
and engage with the techniques of geophysical
survey, for the best results. It is hoped too that
practitioners of geophysical survey will find
them helpful and that, altogether, the guidance
can contribute to raising the consistency and
quality of geophysical survey in archaeological
field evaluation.
Geophysical survey in archaeology continues
to flourish. As of 2006, it is estimated to
be a component of at least 23.4% of all
evaluations arising from planning applications
(http://csweb.bournemouth.ac.uk/aip/aipintro.htm).
The techniques are also finding an increasing
role in the presentation and interpretation
of archaeological sites, in contributing to
archaeological and forensic research, and
in helping to satisfy the demand for media
coverage of archaeological subjects.
Geophysical survey has a wider academic and
professional forum than was the case several
years ago. Since its inauguration in 1995 at
Bradford University in the UK there has
subsequently been a succession of biennial
conferences on Archaeological Prospection,
held in Japan, Germany, Austria, Poland, Italy
and Slovakia, and attended by an ever more
cosmopolitan variety of specialists in geophysics
and remote sensing. The Environmental and
Industrial Geophysics Group (EIGG) of the
Geological Society has similarly hosted a
continuing series of biennial one-day meetings
devoted to recent research in the subject. The
journal Archaeological Prospection, initiated in
1994, has gone on to establish itself as the main
vehicle for publication of relevant research and
case studies; and an International Society for
Archaeological Prospection (ISAP) was initiated
in 2003 (http://www.archprospection.org).
Archaeological geophysics is now a component
of undergraduate teaching in at least 12
universities, although the only post-graduate
degree courses devoted to the subject are
the MSc in Archaeological Prospection at the
University of Bradford (http://www.brad.ac.uk/
archsci/msc_ap.htm) and the MSc in
Archaeological Geophysics recently offered
at Orkney College of the University of the
Highlands and Islands
(http://www.orkney.uhi.ac.uk/courses/archaeology/
geophysics-at-orkney-college-uhi).
Despite the increasing familiarity with methods
and techniques, and a growing number of
practitioners, geophysical survey can be both
a very technical subject, as well as a fertile
area for continuing innovation, commercial
exploitation, and integration with other
prospecting disciplines. It is clear from our
consultations that in these circumstances there
remains a need for independent guidance,
which the following document is intended
to provide – not only for curators of the
archaeological resource, but also for others
who need to know about the potential and
pitfalls in more detail. Our purpose here
is above all dedicated to bettering the
consistency and quality of geophysical survey
in evaluations, especially those arising from
development proposals.
Much of what was presented in the first edition
remains valid and will be re-iterated here.
There are, however, changes reflecting shifts
in thinking and approach that have taken place
over the last few years. To take one example,
the debate on the efficacy of topsoil magnetic
susceptibility as an aid to evaluation, which was
very topical in the early 1990s, has moderated
now that it is increasingly accepted that detailed
magnetometer coverage is preferable, and more
feasible, over yet larger areas. More importantly,
there have been changes in geophysical
instrumentation, technology, methodology and
software, all of which are having an impact on
the choice and performance of geophysical
survey under varying conditions. A particular
example is the great improvement in the virtues
of ground penetrating radar (GPR), now that
software and computing power enable both
greater coverage and production of more
comprehensible display and interpretation.
Another significant development, following
the influential example of European practice,
is the increasing awareness and availability of
alkali-vapour as well as fluxgate magnetometers.
Both types of magnetometer, as well as other
types of sensor, are now being deployed as
arrays on mobile platforms, with considerable
potential to raise the versatility and speed
of ground coverage.
Other areas of rapidly advancing progress
include the further integration of geophysical
data within Geographical Information Systems
(GIS), which has in turn increased the need for
consistency of data geo-referencing and archiving.
In parallel, there are a growing number of survey
projects that seek to integrate ground-based
prospecting methods, together with remote
sensing technologies such as lidar, to maximise
interpretative and analytical potential.
That said, wetlands, alluviated and urban
environments persist as challenges to
geophysicists. While not relevant here, but
to be the subject of future guidance from
English Heritage (forthcoming 2008) it is
worth noting that the remote examination
of the shoreline and seabed is a growing
imperative now that maritime archaeological
conservation is in the ascendant.
The first edition of this guidance was published
in 1995, and this revision is offered in the hope
of maintaining a balanced and independent
view on best practice in the context of progress
since then. With the benefit of much positive
advice, comment and discussion from many
colleagues, for whose patience and advice we
are very thankful, we hope we have improved
the content, and its presentation and clarity.
As the document is available on line
(http://www.english-heritage.org.uk/upload/
pdf/GeophysicsGuidelines.pdf) we expect
to make future revisions and updates more
immediately and easily in future and would,
as ever, welcome comment and advice
towards these.