We did a dowsing experiment with Bristol uni this year.
The south west quadrant of Avebury was grided out and a local dowser set to task while we geofised the same are.
The dowser marked spots of neolithic, bronze aged and medieval sites he detected.
None of them matched up with the geofiz results with showed a large linear mark, proabably a field boundary and aburied stone wall, possibly a farm building and a possible burning pit.