The PiCUS method of Internal Investigation
You can tell a lot about what has happened to a tree by a careful, visual inspection.
However, signs and symptoms that are noticed may suggest problems within the tree where it's not possible to look directly. The Picus Sonic Tomograph is a useful aid in looking deeper into the tree to see if there is decay or problems that need further consideration.
Nails attached to sensors are driven through the bark in a horizontal plane around the circumference of the tree. The sensors measure time taken for sound waves to reach from one sensor to each of the other sensors.
A computer receives this information and displays a cross section of the trunk showing the variations in speed of the sound waves in different colours. The longer the wave takes to travel between sensors the more decayed or damaged the wood or more of an obstruction is present along that path.
A brown or buff colour indicates good quality wood with only minor strength loss. Purple, blue and white colours indicate progressively greater decay or dysfunction, leading to hollows at the white end of the spectrum. Green colours are intermediate and can show the beginning of alterations to wood characteristics or incipient decay.
