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After a desk-based assessment, archaeologists might need to do some
fieldwork to find out more about the surviving archaeology before
developers can get planning consent. Archaeologists can use different
techniques depending on what kind of information they need. These include
ways of seeing under the ground without having to excavate.
Geoarchaeology
This is the study of what the landscape was like in the past.
Archaeologists take a sample from the ground using an auger (rather like
coring an apple) then analyse the microscopic plant, animal and mineral
remains in the soil to reconstruct past landscapes. Sometimes this can
reveal what kind of archaeological remains might be present and where. Done
over a large area, geoarchaeology can tell them how the landscape changed
over time.
Geophysics
In a geophysical survey, archaeologists measure the magnetic field below
ground (magnetometry) and how well the soil conducts electricity
(resistivity). The patterns revealed can help to identify features such as
walls, pits and ditches below ground.
Geomatics
Archaeologists use the term Geomatics to describe the survey of the present
landscape, buildings and structures. Archaeologists use Geographic
Information systems (GIS) and Computer-Aided Design (CAD) systems on
computer and have to ensure that all their surveys are linked to the
Ordnance Survey national grid.
Watching briefs
If a full-scale excavation is not needed on a particular site,
archaeologists may be told to watch over construction work in case anything
unexpected is found. The archaeologists may watch as digging takes place,
to see what kinds of deposits are being disturbed, or record developer's
trenches. At Leadenhall Market watching archaeologists saw that the second
Roman basilica still survives beneath modern basements.
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