Interesting he does not mention the basis of dowsing, the easy way:
The witness and the Similarity Ray
Seems he drowning with the pendulum and witness inside pendulum
..the hard way because pendulum impregnation
Bury some object in your garden like coins or other then get a map from Google Earth and Dowse, look and learn the reactions the pendulum or L-rods have; after learn and know how to search then do the search in another unknow site like a park.