GPR sends out electromagnetic energy as radar pulses that penetrate the subsoil to a depth of up to fifteen meters. When they bounce back, they reveal an image of minute differences in the densities of the subsurface. GPR can detect solid objects, changes in material consistency, and even voids and cracks. It works by reading the reflected signals from submerged structures (the level of detail is governed by the increments of the scan and can be adjusted). Differences in material density and their spatial allocation and depth are subsequently plotted and used to create a full-scale 3-D digital replica of the subsoil that can disclose buried features such as an ancient waterway or the existence of a mass grave. Underground objects are different from the objects on the surface of the earth. Above they are fetishized forms with clear edges and conceptual unity, below they are mere material densities dissipating and flowing into common ground.