The data shown above is from a resistance survey carried out at the site of the Knights Lazarus Hospital, Burton Lazars, Leicestershire as part of a research project.  The grayscale image on the left has been interpolated, which creates a smoother image. The plan on the right is a simplified graphic summary of main anomalies identified.  This survey produced some clear results, including traces of the formal gardens. The graphic summary was produced on the same day as the survey and was subsequently refined for the report.

How does it work?

Resistance surveying involves introducing a small electrical current into the ground by inserting probes into it.  Any resistance to the current as it passes between these probes is recorded by the resistance meter.  This can then be displayed as a plot of high and low resistance values.  It is essential that the probes can actually be inserted into the ground.  Sites covered in concrete, tarmac or similar cannot be surveyed using resistance. Resistance surveying is an 'active' form of archaeological prospection and thus area coverage can be quite slow. For this reason magnetic surveying is usually the prefered choice, unless there is a strong indication that structural remains are present.

What can it detect?

Technically, all it can detect is areas of high or low resistance.  However, features such as buried foundations, roads, paths and demolition or rubble spreads usually produce higher resistance responses.  Lower resistance responses can be caused by features such as ditches, robbed-out foundations and drainage ditches.  The shallow geology of the site can also be detected as both high and low resistance. 

Not all sites are suitable for resistance surveying, and in some conditions a resistance survey may not be possible at all.

(The above images has been reproduced by permission of Grantham Archaeology Group)