Geophysical survey techniques can be useful in identifying a range of different features. It is important to consider the technique being used, and the expected responses of the features being targeted. For example, if a feature does not have magnetic properties, or is not magnetically different from the soil surrounding it, then it is unlikely to be detected through a geophysical survey using a magnetic technique.
Prior to any archaeological survey, you should always consider the location and purpose of the survey and whether the correct technique has been selected for the desired outcome of the investigation.
The interpretation of geophysical datasets is greatly aided through examining supporting information. Before undertaking geophysical survey and analysing geophysical datasets, it is important to review available background historic information about the site and consider the potential site conditions prior to and during survey. Some general considerations may include:
- site conditions (i.e. the ground conditions);
- weather before and during survey (particularly if utilising techniques affected by seasonality);
- archaeological background of the site;
- previously recorded features (Historic Environment Record data);
- features present on historic maps;
- features present on LiDAR survey data; and
- features recorded as earth works or cropmarks on aerial photographs.
The interpretation of anomalies identified in geophysical datasets is generally achieved through the analysis of anomaly shape and strength or increase in values. For example, features with linear, rectilinear, and curvilinear forms are often easier to interpret, whereas features that cause amorphous anomalies can sometimes lack necessary shape or patterning to be conclusively identified.