If all these dowsing devices and remote mineral finding machines were so accurate , dont'cha think the grubberment would have already used them to glom all the treasures we seek ?
Maybe the govmint has the same problem most everyone else has?
I dunno.
I've tried dowsing over a known cache, and I never got a squeak. But my uncle, who has a PhD in physics has dowsed several water wells, and it DEFINATELY works for him. He doesn't know how or why. But it does.