Arbotom Sonic Tree Tomography
Non-Invasive Internal Decay Detection
Sonic tomography is one of the most powerful diagnostic tools available for assessing the internal condition of trees where external inspection alone cannot determine the extent or significance of suspected decay. Urban Tree Management uses the Arbotom sonic tomography system to produce detailed two-dimensional and three-dimensional images of the internal structure of tree stems and branches, providing objective, measurable data that informs risk assessment, management recommendations, and decisions about tree retention across Greater Manchester, Lancashire, Cheshire, Merseyside, and nationwide.
What is Sonic Tomography?
Sonic tomography works by analysing how stress waves travel through wood. A series of sensors are placed at regular intervals around the circumference of the tree stem or branch and connected to the Arbotom unit. Each sensor is tapped in sequence, sending a stress wave through the wood to the remaining sensors. The time taken for each wave to travel between every pair of sensors is recorded precisely and processed by specialist software to produce a tomogram — a colour-coded cross-sectional image of the internal condition of the wood at that point on the stem.
Sound, dense wood transmits stress waves quickly and appears as a warm colour on the tomogram. Decayed, weakened, or structurally compromised wood transmits waves more slowly and appears as a cooler colour. Where wood is absent entirely — in a hollow cavity or crack — waves must travel around the void, taking significantly longer, and the cavity is clearly visible in the image. This allows the user to identify the location, shape, and approximate extent of internal decay or hollow with a level of accuracy and spatial resolution that no visual inspection can replicate.
Wind Load Analysis & Safety Evaluation
In addition to the Arbotom tomography system, Urban Tree Management uses two further Rinntech software modules to support advanced tree risk assessments where structural integrity is in question.
The ArWiLo wind load analysis program allows assessment and analysis of the predicted wind loads acting on a tree's crown, and models how crown reduction pruning would affect the tree's overall stability and safety. Using a photograph of the tree taken in the field, the application maps the crown geometry, calculates crown area and load centre, and derives wind load from these parameters. This provides a quantified basis for recommending crown reduction as a risk management measure in preference to felling, and allows the safety benefit of a proposed reduction to be estimated before works are carried out.
The ArboStApp structural assessment application provides a tool for determining structural strength loss due to defects in stem and branch cross-sections, and assesses anchorage plate losses in relation to canopy size and expected wind loads. While inputs are based on visual observations rather than direct diagnostic measurements, the application produces accurate safety estimates that are sufficient for many tree assessment purposes — and its precision can be significantly increased by incorporating results from Arbotom tomography or Resistograph resistance drilling.
Using Sonic Tomography Alongside the Resistograph
In many investigations it is valuable to use the Resistograph resistance drilling tool as a follow-up to sonic tomography, drilling at one or more of the Arbotom sensor locations to confirm the presence or absence of decay and to refine the tomographic analysis with direct physical data. The combination of non-invasive tomography and targeted resistance drilling provides the most complete and defensible picture of a tree's internal condition available through current arboricultural technology. Urban Tree Management is experienced in using both tools together and in presenting the combined findings in a clear, professionally produced report
When is Sonic Tomography Required?
Sonic tomography is commissioned when an initial visual tree inspection identifies signs that suggest significant internal decay may be present — such as fungal fruiting bodies, areas of response growth, unusual stem geometry, cavities, wounds, or a history of structural failure on the same tree — but where the external signs alone are insufficient to make a confident, proportionate management recommendation.
It is also used to provide baseline data for monitoring known progressive decay over time, to support Tree Preservation Order applications and appeals where evidence of structural condition is required, and to provide objective evidence for insurance purposes or legal proceedings involving tree condition.
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