The data shown below is from a recent survey carried out near Burnham Market, Norfolk for a client who is studying for a Phd with Nottingham University.  The area surveyed was about 4.5 hectares and covered roughly 90% of the site. 

The results clearly show several circular anomalies (darker areas) which are likely to be associated with burial mounds or round houses.  There are also responses which may be associated with habitation, kilns, cultivation and modern disturbance.  A modern water pipe can clearly be seen to the east running NW-SE.

How does it work?

Magnetic surveying measures very small changes in the Earth's magnetic field.  Many human activities can cause a change in this.  Such activities need to physically have the ability to alter the field through heat or disturbance of the soil.  For example, the temperatures involved when firing a kiln can affect the magnetic field in and around the kiln.  Magnetic surveying is a 'passive' form of archaeological prospection and thus is quicker than resistance.  For this reason, magnetic surveying is usually the prefered method for area coverage and is cheaper per hectare than resistance surveying.

What can it detect?

Magnetic surveying can usually detect such things as areas of occupation, pits, ditches, hearths and kilns, but also will react to buried 'modern' items such as nails, agricultural equipment fragments, wire fences or generally any ferrous material in the immediate area.  The geology of the site can play an important role in how successful a magnetic survey will be.  If the local geology is inherently magnetic then it may not be practicable or possible to undertake a magnetic survey.  Similarly, buried services can have an adverse effect on the data.