Galvanic
IP/ERT — Induced Polarisation / Electrical Resistivity Tomography
Galvanic current injection for resistivity and chargeability sections
Frequency band
DC - 10 Hz
Depth range
2 - 500 m
Resolution
High near surface, degrades with depth
Source
Injected DC / low-frequency current
Typical cost
Low to moderate
Survey speed
Slow - electrodes must be planted
Best terrain
Ground where electrodes can be coupled
Domain
Galvanic
Overview
Current is injected through two electrodes and the potential measured across others. Resistivity comes from the steady-state voltage; chargeability comes from the decaying voltage after the current is switched off, which responds to disseminated sulphides and clay.
How the physics works
Apparent resistivity is the measured transfer resistance multiplied by a geometric factor for the array. Building up many overlapping quadripoles produces a pseudosection that is inverted to a true resistivity and chargeability model.
Where it is used
- Disseminated sulphide and porphyry copper exploration
- Groundwater, saline intrusion and landfill studies
- Engineering site investigation and bedrock depth
- Contaminant plume delineation