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Sensor network developed to monitor forests

Germany: Scientists from the Fraunhofer Institute for Microelectronic Circuits and Systems (IMS) developed and installed a new type of system for microclimatic monitoring on the grounds of the Northwest German Forestry Testing Facility in Göttingen, Germany. The new technology enabled differentiated analysis without any bothersome cables. 
“We are using a wireless sensor network so we can measure relevant parameters within an area at many sites simultaneously,” explained Hans-Christian Müller, group manager at the IMS. This way, we receive a very detailed picture about the environmental conditions on site, without much installation effort. Depending on which values they are to measure — for example, soil moisture content, air temperature or the moisture in the leaves — different sensor nodes are inserted into the soil or affixed to branches. If required, the measuring positions can be changed without much effort. The intelligent mini-computers automatically form a network and control the transmission of measurement data within this network. The results are transmitted by cellular radio to a central tree stock database. To facilitate this, a mobile cellular modem is connected directly to the sensor network.
Providing power to the sensor nodes poses a particular challenge. Mounting solar cells to the sensors — a favoured solution in other agrarian and forestry applications — is not an option due to the low penetration of sunlight under the leafy canopy of the trees. That is why, to date, there has been no alternative to batteries that have to be replaced regularly.
A software solution integrated into the sensors ensures that the radio nodes are for the most part in an energy-saving sleep mode. They are active only during the measurement and data transmission process. The measurement intervals can be set to be variable. Parameters that change slowly such as soil moisture need not be measured as often as air temperature, for example, which is subject to larger variations. Since data transmission requires the most energy, the measurement values are calculated as early as the sensor node. This reduces the data volume.
The new technology is already in use in Göttingen as part of the joint project “Smart Forest.” The project aims to optimise forestry processes with the aid of microelectronic components.
Source: Fraunhofer IMS