Non-destructive examination techniques

Trees significantly lower the urban temperature in summer. The contribution of old trees as habitats to biodiversity is even greater than long thought: more than 2000 different species have already been discovered on a single mature oak. Thus, there are many reasons to preserve old trees as long as possible.

However, especially in urban environments, mature trees often have defects (e.g. due to wrong pruning or root capping), which can endanger the stability. Therefore, we need nondestructive examination techniques to assess the condition of trees and methods to evaluate their stability on the basis of the measurements. For the technical examination of trees, two methods developed and patented by RINNTECH® in the 1980s and 1990s, have proven their worth, especially in combined application: sonic tomography and resistance drilling.

ARBOTOM® sonic tomography shows the remaining load-carrying parts of defective cross-sections and the percentage loss in load-bearing capacity compared to the intact situation.

Soil analysis with the ArboRadixTM extension of the sonic tomograph can be used not only to determine the size of the statically effective root plate in order to evaluate uprooting safety, but sometimes even to determine the position and course of statically relevant lateral roots in order to avoid injuries during ground works.

The profiles of the real RESISTOGRAPH® resistance drills (which only come from the original inventor and developer RINNTECH®) provide information that no other method has been able to determine so far:

• The profile-transition from intact to deteriorated wood indicates the tendency of the fungal decay to spread: here one can see whether the tree has succeeded in compartmentalise the decay or whether the fungal degradation is spreading outwards;

• Drillings in an angle into the buttresses show whether there are root-borne fungi that degrade the wood under the base of the trunk and thus may endanger the stability;

• Even in the crown, critical spots can be examined quickly and efficiently with the light device (weight under 4kg): you can hold on to the ladder or climbing side with one hand and carry out the measurement with the other;

• In many species, the tree-ring growth rates are indicated allowing to estimate the future thickness of the shell walls;

• The internal memory stores up to 10000 profiles, which can be printed out in 1:1 scale during the drilling or also displayed in high resolution on a smartphone’

The results of such examinations are then the basis for the evaluation of stability using the “Allometric Self-Referencing” method, which has proven to be better and more reliable than VTA (Visual Tree Assessment) and SIA (Static Integrated Assessment): the ArboStAppTM makes it possible to carry out the final assessment at the tree, but still document it in a comprehensible way.

For more information on examination techniques visit or call (02) 6772 6770. AA

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