Arbotom Sonic Tomography Picus
Arbor Cultural provides sophisticated tree health detection expertise in the form of Arbotom sonic tomography (sometimes called Picus). Technology has moved on quickly and there are now several manufacturers with equipment that provides this assessment albeit with slight differences in the method of assessment and the interpretation of results.
Arbor Cultural believe that ArboTom and the Rinntech suite of products offer the best solution in sonic tomogralphy. We work with private residential homeowners in and around the South East who
need specialist tree reports and surveys to obtain planning permission. We also undertake work for commercial and public sector clients.
What is Arbotum Sonic Tomography?
In brief, sonic tomography uses the speed of sound waves to detect different wood densities in trunks, stems, and branches.
Degeneration and rotting can weaken the wood, but in many cases, it may not be
extensive enough to be of concern or compromise a tree’s safety. The issue is that without invasive drilling or boring — which could further result in openings for decay organisms that will potentially weaken their integrity further. This equipment enables us to know how structurally sound it is.
And thus, how best to proceed.
Step forward, the ArboTom Tomograph.
This is a highly precise, non-invasive instrument for tree risk assessment.
The Tomograph quickly analyses a tree trunk’s internal condition, thus evaluating the quality of the wood. The results are visual, enabling easy interpretation to decide the next steps, if appropriate: the Tomograph produces a colour-coded two or three-dimensional picture that shows zones of different sound transmission properties.
In Arbor Cultural’s experience, it’s the most thorough technology for detecting tree decay. Ultrasonic velocity has been shown to be extremely sensitive to the early stages of wood degradation.
Plus, if used with ArboRadix, it can detect the spread of a tree’s roots below ground.
How Does It Work?
In a nutshell, sound waves pass through wood.
Sensors attached to the tree measure the time it takes an impulse to travel through the wood to reach other sensors. Thus, the data collected is sent to a tablet computer, which creates a graphic image showing the tree’s cross-section.
- Solid, sound wood shows as green, with degradation and loss of solidit displayed in orange. Significant decay, degradation or cavities present as red to purple.
- The computer reveals each tree’s safety factor; also the direction in which mechanical loss is going, and its percentage.
- Equally, we can be ultra-precise and more localised: with a Resi PD micro drill, Arbor Cultural can investigate specific areas of a tree
However, the following is important:
To complement our expertise, the Tomograph is a powerful tool that provides extra information and guidance. As arboricultural consultants, we use sonic tomography to inform and support our professional opinion on a tree’s health – rather than a definitive assessment in its own right.
We take this information and input it into the ArboStApp wind load modelling
software. This will further assist us in assessing the risk of tree or branch failure
and proposing the extent of any remediation measures required to reduce this risk.
If used in conjunction with ArboRadix it can even detect roots below ground.
How would Arbor Cultural’s expertise on your trees help you obtain planning permission?
THE
PROCESS
Sound waves travel through sound wood. Sensors around the tree measure the time it takes an impulse to travel through the wood and reach the other sensors. The collected data is simultaneously sent to a computer, which turns the data into a coloured image to visually represent the trees cross-section.
The sensitivity can be adjusted for different types of tree structure in terms of non-porous, diffuse porous ring porous or semi-ring/diffuse porous. It can also be adjusted for different species of tree. This can be used to present a clearer and more accurate interpretation of the structural condition of the inside of any tree. This is a fast and easy to set up test, that is non-invasive and non-destructive.
It is the only device on the market to measure at different heights of the tree simultaneously. The sensors are set at two or three separate horizontal levels and the acoustics across and between the levels is recorded. This allows it to produce a genuine three-dimensional interpretation of the internal condition of the tree.
The process is fairly simple. The area around the base of the tree is cleared at the height that is to be tested. This can include removing any epic comic growth or suffering as well as surrounding vegetation and man-made materials so that possible to get all the way around the tree.
North is established and is usually taken as the location for sensor one and a nail is driven through the bark into the wood of the tree. Then additional nails are inserted at the same height all the way around the tree with gaps of between 150mm and 400mm with nails put in wherever there is a significant change in the diameter of the tree. This will go on either side of the cavity as well as on the outside of any roots bulges or extending buttress roots. Each level can have up to 24 sensors with the standard pack and if two levels are being assessed same time that would be an average of 12 in each on each and if three levels then an average of eight.
Once all the nail locations have been located in three dimensions and input into the computer then sensors are placed on the nails and connected up to one another and the power supply. At this point the striking point on each sensor is tapped 7 to 10 times to undertake the test.
This will result in a visual display on the computer showing the areas of sound would and decay with sound wood represented by green, degradation and loss of solidity represented by the orange colours and significant decay degradation or cavities represented by the red colours.
The computer will also show a safety factor for the tree and the direction and percentage of loss of mechanical strength with the direction displayed by directional arrow.
It will also show the path to each of the different sensors with these colour-coded in the same way as well as assessing the trunk strength based on its cross-section as compared to a perfect cylinder of the same diameter.
This data can be input into the ArboStApp package to assess the wind load of tree. Further assessments can be done of the spread of the roots with the addition of the Arbor Radix sensor and software.
It is also possible to investigate specific areas of a tree with a Resi PD micro drill, would drill or trunk corer, as a result of identifying targeting key areas using the sonic tomography information
These results images and charts can be used by experienced tree consultants to better inform their professional opinion. In no way should they be seen as definitive in their own right and are only there to provide additional information and guidance.
