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Earth Observation



Tools and Methods

Time-lapse electrical resistivity tomography (ALERT)

An innovative 4D electrical imaging system known as ALERT (Automated time-Lapse Electrical Resistivity Tomography) has been developed by BGS which uses permanent in-situ electrode arrays and “smart” microprocessor-controlled instrumentation to remotely monitor temporal changes in subsurface properties. Such changes may be related to changes in fluid flow, hydrogeochemistry, or saturation levels. Complex dynamic processes can now be studied at unprecedented sampling rates without manual intervention. Volumetric images of the shallow subsurface are captured “on demand” by wireless telemetry (GSM/3G, GPRS, satellite and/or internet) from an office PC or laptop anywhere in the world – thereby eliminating the need for expensive repeat surveys. A centrally managed network server and web-portal are used for data capture, processing, modelling, visualisation and databasing. The entire process from data capture to visualization is automated and seamless. It is proposed to install ALERT technology at a site in the Witbank Coalfield, South Africa to:

To-date, none of the above applications have been tested or demonstrated in areas impacted by mining.