Abstract. In the last decade, reconstruction of plant dimensions and volume has gained a noticeable importance, in particular for the possibility of collecting data correlated to biomass, leaves area, etc. This is specifically of interest in the case of vineyards, where knowledge of variability can be not only a useful mean to evaluate the health condition of the vines and of the grapes, but also an important input to allow variable management practices. Different sensing technologies are available for shape reconstruction, as for instance ultrasonic sensors, laser scanners or depth cameras, however, their practical application is still limited by low quality information, high costs, or high speed data processing demand. For the present work two-dimensional imaging is proposed as a viable solution for shape reconstruction of canopies. The method takes advantage of low cost 2D commercial cameras, which can be installed on board the tractor allowing on the go collection of images of plants from the bottom. The paper describes the instrumentation set up and integration with a specific thresholding algorithm allowing segmentation of canopy profile. Tests were carried out on 20 different dates on a glera vineyard in an experimental farm in the North of Italy. The results were correlated with the number of leaves, leaf area index and canopy volume. High correlation was identified in the case of volume with coefficients of determination R² > 0.7 in most of the cases.Keywords: canopy, profile, imaging, segmentation.
IntroductionThe opportunity of analyzing the variable profile of vineyard canopies is of the highest relevance for the possibility of precisely quantifying local biomass. Such interest arises from the correlation, which is typically found between the canopy size and plant needs in terms of water and nutrients as well as with the yield and quality [1]. As a consequence, knowledge of plant dimensions allows not only evaluation of the plant health conditions, but also exploitation of variable rate and management practices, including crop protection and canopy management [1][2][3].Many researches and approaches have been proposed in the last decade, which allow quantification of the plant dimensions [1; 3; 4], also taking advantage of the availability of miniaturized low cost sensors and of an increased speed in data processing [5; 6]. Available technologies can be referred mainly to ultrasonics, laser sensors and other optical methods [7].Ultrasonic technology is a low cost solution, which relies on the sound waves echoing off of a given target [8; 9] to provide its external contour. Its performance is influenced by ultrasound propagation, which often exhibits parasitic signals or losses especially in the cases of thin targets or high reflection angles, as is in the case of small branches or in the case of badly oriented leaves. Additionally, ultrasonic sensors are very much sensitive to humidity, dust and high temperatures, however, their practical implementation has provided interesting results especially cou...