You have to look very closely to see it: an orange cable with an electrode the size of a tent peg every 50 meters. At this moment, a so-called long ERT measurement is taking place in the rural areas of the Walloon municipalities of Aubel, Herve, and Dalhem.
The letters ERT stand for ‘Electric Resistivity Tomography.’ This is an electrical resistance measurement used to further map the structure of the soil. Along the entire 7-kilometer measurement route, a 5mm thick cable is manually laid. An electrode is attached to it every 50 meters. The researchers generate a weak electric field in the subsurface for a short period. This way, the electrical resistance in the subsurface is measured.
This measurement is carried out by the University of Liège and is part of the E-TEST project, intended for the Einstein Telescope. It involves a route along the Berwinne River from Thimister-Clermont through Val-Dieu to near Mortroux.