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Performance of an Ultrasonic Ranging Sensor in Apple Tree Canopies
Department of Agro-Forestry Engineering, University of Lleida, Av. Rovira Roure, 191. 25198 Lleida, Catalonia, Spain
Department of Agriculture, Livestock, Fisheries, Food and Environment, Center of Agricultural Mechanization, Generalitat de Catalunya, Av. Rovira Roure, 191. 25198 Lleida, Catalonia, Spain
Department of Agro-Food and Biotechnology Engineering, Polithecnical University of Catalonia, Av. Canal olímpic, 15. 08860 Castelldefels, Catalonia, Spain
* Author to whom correspondence should be addressed.
Received: 13 December 2010; in revised form: 19 January 2011 / Accepted: 14 February 2011 / Published: 28 February 2011
Abstract: Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and optical sensors are the most used for this purpose. The objective of this work was to assess the performance of an ultrasonic sensor under laboratory and field conditions in order to provide reliable estimations of distance measurements to apple tree canopies. To this purpose, a methodology has been designed to analyze sensor performance in relation to foliage ranging and to interferences with adjacent sensors when working simultaneously. Results show that the average error in distance measurement using the ultrasonic sensor in laboratory conditions is ±0.53 cm. However, the increase of variability in field conditions reduces the accuracy of this kind of sensors when estimating distances to canopies. The average error in such situations is ±5.11 cm. When analyzing interferences of adjacent sensors 30 cm apart, the average error is ±17.46 cm. When sensors are separated 60 cm, the average error is ±9.29 cm. The ultrasonic sensor tested has been proven to be suitable to estimate distances to the canopy in field conditions when sensors are 60 cm apart or more and could, therefore, be used in a system to estimate structural canopy parameters in precision horticulture.
Keywords: ultrasonic sensor; distance measurements; apple tree orchard; ultrasonic interferences
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Escolà, A.; Planas, S.; Rosell, J.R.; Pomar, J.; Camp, F.; Solanelles, F.; Gracia, F.; Llorens, J.; Gil, E. Performance of an Ultrasonic Ranging Sensor in Apple Tree Canopies. Sensors 2011, 11, 2459-2477.
Escolà A, Planas S, Rosell JR, Pomar J, Camp F, Solanelles F, Gracia F, Llorens J, Gil E. Performance of an Ultrasonic Ranging Sensor in Apple Tree Canopies. Sensors. 2011; 11(3):2459-2477.
Escolà, Alexandre; Planas, Santiago; Rosell, Joan Ramon; Pomar, Jesús; Camp, Ferran; Solanelles, Francesc; Gracia, Felip; Llorens, Jordi; Gil, Emilio. 2011. "Performance of an Ultrasonic Ranging Sensor in Apple Tree Canopies." Sensors 11, no. 3: 2459-2477.