Sonic Tomography

Decay in trees can weaken wood enough to increase the chance of mechanical failure. However, in many instances decay is not extensive enough to compromise the safety factor of the tree. The use of both Picus and Arbotom sonic tomography enables the extent of decay to be assessed without invasive testing such as resistograph drilling or boring, which damages trees and potentially impairs the tree’s ability to compartmentalise the decay.




Sonic tomography uses relative velocity of sound waves, induced across the stem of a tree, to construct a two-dimensional picture (tomogram) that shows zones of different sound-transmission properties. The zones are colour-coded and indicate degrees of degradation and the presence of hollows. One advantage of the Arbotom system is that the software that accompanies it enables the data collected during each test to be used to calculate strength loss.



Arbotom sensors positioned around the stem of a pine tree.
Tree expert using the Arbotom impulse tomography unit



Paul Melarange is probably the only tree consultant in the country to integrate the information gathered through sonic tomography with the ‘Tree Statics Model’. In tree statics, the ability of a tree to withstand wind loads of gale force is calculated by including the shape of the load-bearing structure (trunk and crown), the properties of green wood and the forces that occur in a gale-force wind gust. The influence of the reduced cross-sectional area, resulting from decay and measured by the tomography, can be incorporated into the tree statics evaluation. The combination of the two enables a more objective assessment to be made of the tree’s fracture stability. The result is presented as a safety factor, which can be used to indicate whether or not remedial action is required.



The partially failed root plate of a beech tree that has re-stabilised

Tree stability testing

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Arbotom sensors positioned around the stem of a pine tree.

Tree condition & risk assessment

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Picus tomogram showing the extent of a large cavity at the base of an ash tree
The sensors of a Picus sonic tomography unit positioned around the base of an ash tree




  • Coloured images (tomograms) produced from each test show clearly the extent of any decay present.
  • The combination of Sonic Tomography with Tree statics enables a more objective assessment to be made of the tree’s fracture stability.
  • Picus and Arbotom tests are both non invasive methods as opposed to other decay detection procedures such as resistograph drilling.
  • The accurate recording of the level at which the test was carried out and the locations of the individual measuring points ensures the tests are repeatable, enabling comparison between previous and subsequent tomograms.


Results can be presented in a detailed report or as a short test protocol that is suitable for tree officers, consultants and arborists to interpret independently.



Contact us for more information or to discuss your requirements



T: 01865 400759   E:


Thinktrees Ltd

8 Swinstead Court



OX44 7TG