Petr has asked the right question. Why are they out their with their fancy gadgets? What do they hope to find.

Several times people have used the term "local history", as in they are well versed in local history. Where do they think that knowledge came from? Also, the professionals are out there with more than a good knowledge of local history. They also know the theories that are based on the razor edge of evidence. Their dig may be the one that pushes a theory over on to either the side of knowledge or that of the unproved theory.

Another point is that archaeology is based on so much more than a pot sherd or cave painting. There are whole bodies of knowledge based on findings seed and pollen found in the right place. We know a lot about the climate of the earlier years based on the evidence found through the meticulous digging, millimeter by millimeter through layers of history.

This is not something the hobby hunter can do or should try.