I want The Salvage to have some sort of sensor that can help guide the player to regions underground that could be of interest, but how could one glean some idea of an anomaly’s shape, size, and nature?
Two ideas I came up with are for probes that can detect cavities underground, along with solid objects (i.e. things that cannot be dug through). The first type plunges down until it hits an open area, where it expands to describe the basic shape of that area, much like filling a balloon inside an oddly shaped enclosure. The second type sends a kind of wire or cable down until it touches a solid object,. It then slips over the side until it can reach another vertical drop. This not only indicates that there is a solid object buried, but also hints at the shape of that object.