From all this information, nine times out of ten there is a short list of missing persons from which a positive ID can now be made. 1.2 Geophysics Archaeology uses geophysics to detect underground anomalies such as remains of buildings, or the signature of field workings such as ploughing where the soil has been disturbed and has not been compacted to the same density as the surrounding soil. It is possible for an archaeological geophysicist to identify smaller anomalies such as pits and post-holes. In archaeology, geophysics is used to identify a site and decide which areas to start investigating. Similarly, in crime scene work the use of geophysical equipment would allow a survey of possible areas of buried evidence and help to pinpoint further areas of interest, saving police from spending time searching or excavating large areas.
Geophysics can also identify graves, metal and other buried objects.
The necessary equipment is expensive and would not be used often enough by police to justify purchase. However, such equipment is accessible to most archaeologists, who are either themselves experienced in its use, or in contact with others who are. 1.3 Survey Mapping of a site is something that archaeologists do as a matter of course. An EDM is used to make very accurate maps. The information is downloaded into a computer, which can produce a map onto which further information can be added, such as different symbols for different types of object or biological remains found at a particular point.