Electrical Resistivity
Definition
The resistance of a volume of soil to electrical current flow. Wet, clay-rich, or decomposing organic material has low resistivity. Dry sand and gravel have high resistivity. Graves often show low resistivity relative to surrounding substrate.
- Measures
- Resistance of soil to electrical current
- Low resistivity
- Wet, clay-rich, decomposing organic matter
- High resistivity
- Dry sand and gravel
- Forensic use
- Grave detection relative to substrate
Common questions
Why do clandestine graves typically show low resistivity compared to undisturbed ground?+
Grave fill is usually disturbed and more porous than the surrounding soil, and it retains moisture and decomposition fluid from the buried remains, both of which lower electrical resistance, producing a contrast that a resistivity survey can detect.
What can cause a false positive in a resistivity survey?+
Any localised change in moisture or compaction unrelated to a grave, such as a buried root system, a filled ditch, a utility trench, or seasonal water pooling, can produce a similar low-resistivity anomaly, so results are normally confirmed by ground-truthing.
Related terms
- Dielectric Permittivity
- A soil's capacity to store and transmit electric field energy. Higher water content raises permittivity and slows the radar wave. The contrast...
- Magnetic Susceptibility
- A measure of how strongly a material is magnetised by an external field. Topsoil heated by fire or biological activity has elevated...
- Multi-Method Survey
- The deployment of two or more independent geophysical methods over the same search area. Anomalies confirmed by multiple methods carry higher confidence...
- Physical Contrast
- The difference in a measurable soil property (density, susceptibility, resistivity, permittivity) between a target and its surrounding host material. No contrast means...
- Signal-to-Noise Ratio (SNR)
- The ratio of anomaly amplitude to background variation. Pipes, cables, rocks, roots, and instrument drift all add noise. A target is detectable...