Detect what's in the void
 

Hello, everyone! Is there any way to detect the contents of a void, say, the size of a tomb, where the location is known, just to be sure there's something inside

hi

There is such a development on ultrasonic waves. And although this is only a prototype, it successfully detects waves, concrete slabs, metal objects and non-ferrous metals, voids at a depth of 5 meters. The best detection is in damp ground after heavy rains or in early spring when the snow melts. In dry ground, the sensitivity is reduced by about 1 meter.