Dan Cole

A ground-penetrating radar unit known as SIR being pulled across the surface near an excavation area at Lahav, Israel. Continuous electromagnetic impulses aimed into the ground send back “echoes” when they encounter changes in the composition of subsurface materials—a stone wall, for example, or a cistern. The operator presses a hand-held button as the machine passes over premeasured marks on the ground. This adds vertical lines on the printout record to indicate exactly where “echoes” have located a possible feature.