Archaeologists use many different methods to gather information about the past. Most archaeological projects follow a similar pattern: first an area or site has to be surveyed and mapped and its contents recorded in detail. Archaeologists use a range of equipment for surveying, including handheld GPS (Global Positioning System) units, dumpy levels and Electronic Distance Measuring (EDM) devices, so that they can plot detailed information about the location of artefacts and the shape of sites.
Excavation or artefact collection can only take place once the archaeologist knows as much as they possibly can about a site, its contents and its history. Excavation is usually (but not always) done by hand so that the removal of material from a site can be carefully controlled. Excavated soil has to be sieved for artefacts, samples collected for later analysis, and all artefacts cleaned, catalogued and stored. Once an excavation is completed all of the artefacts have to be taken back to the laboratory and analysed in detail. As a rule of thumb, for every one day that an archaeologist spends in the field excavating, they will spend three days in the lab making sense of it all.
Geophysical survey methods have become an important part of the archaeologist's toolkit, because they provide a glimpse of what lies beneath the soil surface without excavating. Ground penetrating radar, magnetometry and electromagnetic conductivity devices all provide different methods of 'seeing' beneath the ground. Depending on the device they can find features such as middens, pits and graves, or structural features such as walls and floors. Any 'anomalies' revealed by the geophysical survey can then be targetted for proper hand excavation to see what they contain.