Ground Conductivity has the advantage of not requiring probes to be placed into the ground. This means soil conductivity (and hence resistivity) can be measured over hard or high resistance surfaces.
Ground Conductivity can be used for a number of applications:
- Detection of buried metal objects
- Detection of cavities
- Contaminated land mapping including plumes
- Buried foundations and mine shafts
- Geological feature mapping.
Swallow holes investigated using ground conductivity
The appearance of a hole in the middle of a school playing field understandably caused concern to the local education authority who commissioned a survey to investigate the area for further swallow holes in the chalk geology.
The survey was carried out using ground conductivity (EM31). The plot shows the vertical quadrature data collected with a notable high conductivity anomaly present to the right of centre. The results were interpreted as high conductivity occurring where saturated gravels are present over the chalk. It is likely that groundwater within the gravels has moved down to the chalk and is aiding the formation of solution features. As this groundwater flow in the gravels.