Wageningen UR Greenhouse Horticulture has developed two prototypes of measuring equipment for automated tree girth measurement for PPO Nursery Stock. This autumn these prototypes will be tested and compared in practice.
The stem diameter at one meter above soil level determines the grading of avenue and fruit trees. Tree-nurserymen are annually measuring this diameter to gain insight into their stock and to be able to make arrangements with clients. Such measurements are labour-intensive and they have also been found to be difficult to standardise.
Automation of tree girth measurements is therefore desirable. Wageningen UR Greenhouse Horticulture has tested four measuring devices in a first study. Two of these were found to be suitable for further development, the Epicom and the Perimeter. The Epicom is reliable and the Perimeter is handy and robust. An electrical version of both devices has been developed which automatically transmits the recorded data to a central computer on the holding via a datalogger. The prototypes of the Epicom and Perimeter are after further development now ready for practice and will be tested in the field in August and September.
Epicom
The Epicom conducts the measurement with the tape measure but in a mechanical fashion. The device surrounds the stem via two beaks and places a measuring tape around the stem. The device then measures the length of the tape required to surround the tree. This is the circumference of the tree. Measurement with a tape measure gives the best results because the tape can fold around irregularities, giving the circumference of the stem.
Perimeter
The Perimeter is based on a triangulation in which a circle falls with the three sides of a triangle touching the circle at three points. The diameter of the enclosed stem can be determined from this triangulation via a mathematical equation. The construction of the Perimeter is very robust and requires no special training for use in practice. The coloured bands enable easy reading of the calibration and the measured class can immediately be read.
This research is financed by the Netherlands Ministry of LNV (Agriculture, Nature and Food Quality), Directorate Regulations (Innovation Regulation), Flowers & Food, Foundation Innovation Platform Nursery Stock, Agricultural Innovation Noord-Brabant, Huverba BV and M. van den Over Boomkwekerijen BV.