Geophysical survey is a general term for a range of non-invasive or non-destructive techniques used to detect features buried beneath the surface without digging. A range of approaches exist using specialist equipment to measure variations in the physical properties below the surface to identify archaeological features. Depending on the type of survey being conducted structural elements, traces of human activity or structures can be identified as they return significant anomalies in the data from the background values.
However if no particular contrast can be identified then no archaeological feature can be detected. For this reason it is important to use a survey strategy that includes a number of complementary techniques each measuring a different property of the soil.