Geophysical surveys are an important part of the initial assessment of a site or site complex. By 2006 nearly one third of all site evaluations in Great Britain used geophysical methods. It is not just an add-on to more traditional methods but is an essential tool used to minimise the risk of accidental discovery.

The presence and absence of sites, the full underground extent of a site and the nature of the site can all be explored with geophysical methods.

Geomagnetic surveys dominate geophysical survey methods as they are reliable in a wide range of soil conditions, are well matched to most New Zealand and Australian sites, and cover large areas in a short time. Geomagnetic surveys are probably the most cost-effective geophysical method in an archaeological context.

ASL is the only archaeological consultancy with in-house equipment and experience in archaeological geophysical surveys in Australasia. For the past decade Hans-Dieter Bader has developed geomagnetic surveys from a research method into a reliable and effective tool in commercial contracting archaeology.