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The Warsaw Voice » Other » July 1, 2009
Biology
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Non-Invasive Tree Scans
July 1, 2009   
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Researchers at the Warsaw Institute of Electrical Engineering (Instytut Elektrotechniki) have developed a tomographic system to examine trees without cutting out samples from them.

The system-designed with the help of scientists from Wrocław and IT specialists from the ŁódĽ University of Technology-has won a gold medal at the iENA international exhibition for inventors in Nuremberg, Germany, and a certificate of distinction from the Polish science minister.

The system is composed of a measurement device and software to enable examination of cross-sections of tree trunks.

The conventional method for evaluating the health of forest stands and individual trees in parks is more invasive because tree experts examine samples cut out from tree trunks.

Diagnosing trees
Foresters, dendrologists and specialists taking care of forests and parks need to evaluate the condition of tree trunks swiftly and correctly. If a flaw is detected in the structure of the tree this probably means that the tree has been attacked by a disease caused by fungi or insects.

Apart from being worse material for industry, sick trees are weaker and more prone to being broken by strong winds. To ensure safety to property and people, such trees should be cut down on time, especially in built-up areas.

In conventional methods, trunk samples are taken to check the condition of the trunk structure. The problem is that this sometimes invites fungi or insects to attack the site of the cut, says Andrzej Sikora, D.Sc., of the Wrocław branch of the Warsaw Institute of Electrical Engineering.

Besides, the traditional method allows specialists to learn about the condition of the tree only in the area from which the sample has been taken, says Piotr Reda, Ph.D., of the Department of Biological Sciences at the University of Zielona Góra. The diameter of the cylinder-shaped sample is usually around 0.5 centimeters. "If the tree was attacked by disease in a different place the specialists will learn nothing," Reda says.

Nothing but pluses
According to Przemysław Berowski, D.Sc., who heads the research project, the new method is far more effective than traditional methods. It is less invasive and provides information about the condition of the tree in the whole cross-section of the trunk. The measurement electrodes are only stuck in selected points, doing minimal damage to the layer under the bark, Berowski says.

The measurement system is controlled by a microprocessor. By means of 16 electrodes, the device generates appropriate currents and measures the distribution of electric potentials in the trunk. To reconstruct the trunk's structure, interferences and linearly dependent measurements have to be eliminated from the collected data by digital methods for signal analysis.

The system is controlled by a computer with specialist software. "The algorithm is supposed to make it possible to check the distribution of conductivity inside the trunk on the basis of voltages measured on the outside. The place where the tree is damaged has zero conductivity," says Magdalena Stasiak, D.Sc., of the ŁódĽ University of Technology. Her colleague Piotr Dmuchowski, M.Sc., seconds, "Such a conductivity map makes it possible to determine the structure of the whole trunk."

For the time being, the scientists are working on a prototype device the size of a small suitcase. They say the system will be mobile and resistant to weather conditions. It will be powered by batteries.

Work on the project began last year, attracting considerable interest among foresters, who will be able to use the device to select trees for use in the furniture industry and protect forest stands against disease without damaging healthy trees in the process. Dendrologists are also interested. They hope to use the system to determine the age of trees.

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