A powerful archaeological technique to systematically sample the upper surface of cultivated or disturbed ground in an effort to locate or map the distribution and extent of archaeological sites. The basic assumption is made that the topsoil contains distinctive traces of archaeological activity—fingerprints of what has gone on in the past. In this sense the topsoil is treated as a single extensive open archaeological context. It includes material that has been deposited onto or into the topsoil from above, for example debitage from an episode of flint knapping by someone sitting on the ground. It also includes material from features underneath the topsoil that are exposed to the effects of cultivation or ground works and therefore mechanically brought into the ploughsoil. Cultivation will have mixed all these different sources of material together, and a proportion of what is in the soil will be visible on the surface.
There are two main ways of carrying out fieldwalking. The first is line walking, where linear transects are defined at fixed intervals and the fieldwalkers traverse each line collecting material that they see within their corridor of vision. Lines are usually divided into stints (often the stints are the same length as the gap between transects to make data processing easier) and the material recovered is bagged by line and stint. The second technique is grid walking, where the survey area is divided into squares and the walkers spend a fixed amount of time working in each square gathering everything they can see during the allotted search period. At the end of the allotted time the finds are bagged together and the team moves on to the next square. In both systems it is important that each sample unit (a line stint or a grid square) is treated equally, otherwise the results will be worthless. After the finds have been collected, cleaned, sorted, and identified, different categories can be mapped and patterns identified.