FAQ Treetronic
Last Updated on Tuesday, 01 December 2009 06:52
What is the difference between Sonic Tomography and Electric Impedance Tomography?
Sonic Tomography uses sonic waves to obtain “mechanical” information about the wood of the tree. Electric impedance tomography uses electric current to gain “chemical” information about the wood. In short, two different types of information are obtained by using these two different methods.
What are the limits of electric impedance tomography?
The EIT data measured are ambiguous; several resistance distributions in a tree can cause the same readings on the circumference. Therefore, the electric impedance measurements may not show the correct results in the following situations:
1. Measurements close to ground level. The EIT calculation assumes the (infinite) extension of the tree above and below the measuring level. This condition can not be fulfilled when measuring close to the ground because the cylindrical cross-section of the trunk develops into the root system beneath ground level. However, particularly in highly conductive wood near/under ground level (such as can be found in trees with a fungus infection), this will be shown correctly.
2. Hollow trees. The remaining ring of wood is very conductive compared to the hollow centre of the tree. The calculation may not be able to identify the cavity correctly (the cavity should have high resistance) if the distance between the measuring points is too large.
3. Water-filled cavities. A cavity filled with water could be shown with blue colours (high conductive) in the EIT.
What is the difference between Shigometer and Treetronic?
Both Shigometer and Treetronic try to get the same information about the consistency of the wood (“what is the electric impedance?”), but the working principle is different. The Shigometer required you to drill a hole into the tree and it collected the information about the wood along the drill-line. This is a direct conductivity measurement, meaning two electrodes touch the wood in order to measure voltage and current.
The Treetronic uses a more accurate 4-electrode setup. Two electrodes are used to get the current into the tree; two other electrodes measure the drop of voltage at a different position. In doing so, the Treetronic can collect data of the entire cross section. In the strictest sense, this is data of a column of the tree).
The calculation of the Treetronic are also very different from those of the Shigometer. The results of the Treetronic measurements are recorded in an Electric Impedance Tomogramm (EIT). Interpreting an EIT requires experience and knowledge of the particular species of tree. An EIT can provide valuable additional information about the type of damage in a tree.
Example: When measuring a beech tree with Meripilus giganteus, the sonic tomograph will not be able to detect this fungus well because the wood in the stem is not affected by the fungus growth. The Treetronic would show very high conductivity which, in beech trees, is a clear indication for a fungus infection that increases moisture content. In this case, the Treetronic can also provide you with a look underneath the ground because of the 3-dimensional nature of the measurements. The sonic tomograph does not give you any information from below the ground level.
How many probes do I need to use the Treetronic?
The number of Treetronic channels or probes is 24. Electric impedance tomography requires more measuring points than sonic tomography in order to get good resolution. In many situations it is best simply to double the number of sonic measuring points in order to get a good electric impedance reading. For instance, if the sound tomogram was recorded with 10 measuring points, the electric impedance tomogram should have 20 probes. You can measure larger trees by combining up to 3 Treetronic instruments.
How important is the exact geometry?
The EIT Tomograms do need accurate geometry information about the measuring level.
The more accurate the geometry of the measuring level is, the more accurate the tomograms will be. The PiCUS software offers you a number of functions to measure the geometry efficiently. The triangulation method is most accurate.
Do the instruments require annual servicing?
No. The sensors do not need to be calibrated regularly, but argus does offer check-up and maintenance services according to the regulations ISO9000 and others.
Do I need training to operate the PiCUS Treetronic unit?
Yes. Training on the instruments is highly recommended and will take 1 or 2 days.
Do the tomograms show sapwood – heartwood of the trees?
Yes. Particularly the Treetronic shows you the sapwood / heartwood accurately in many situations. In trees with defects (decay or cavities), the sapwood – heartwood is more difficult to find.
Can I see growth rings in the tomograms?
No. Growth rings are much too small to detect with this technology.
Do the tomograms give me any information about the roots?
The sonic tomograms (SoT) do not give you any information about the roots. They only give information about the level of tomography.
The electric impedance tomogram (EIT) produces an integral of the resistance of a certain section of the tree. The length of this section is approximately equal to the diameter of the tree itself. Thus the EIT can give you information about the roots when you measure near ground level, particularly about the decay in roots.