Geophysical Survey at Land at Polehanger Lane, Hemel Hempstead

Data was collected using a cart carrying four paired Bartington magnetic sensors. Four sensors mounted 1m horizontally apart and very accurately aligned to nullify the effects of the earth's magnetic field. Readings relate to the difference in localised magnetic anomalies compared with the general magnetic background. Each data point is geographically referenced using an on-board Trimble RTK survey grade GPS system. Readings were taken at 0.125m centres along traverses 1.0m apart. Readings relate to the difference in localised magnetic anomalies compared with the general magnetic background. The magnetometer survey has not recorded any magnetic responses that could be interpreted as being of archaeological interest. The survey has recorded the locations of 20th Century building foundations in Areas 1 and 3, which correspond with buildings that are visible on historic mapping. Responses of uncertain origin have been identified across the data; they are probably due to natural and modern processes. Uncertain zones of increased response could be infilled chalk extraction pits. Former field boundaries and two service pipes have been recorded in the survey. Discrete anomalies and zones of increased magnetic response are due to variations in the underlying geology.