title: Performance of an ultrasonic ranging sensor in apple tree canopies.
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.
authors.affiliation: Department of Agro-Forestry Engineering, University of Lleida, Av. Rovira Roure, 191. 25198 Lleida, Catalonia, Spain. AEscola@eagrof.udl.cat
authors.forename: Alexandre
authors.initials: A
authors.lastname: Escolà
authors.forename: Santiago
authors.initials: S
authors.lastname: Planas
authors.forename: Joan Ramon
authors.initials: JR
authors.lastname: Rosell
authors.forename: Jesús
authors.initials: J
authors.lastname: Pomar
authors.forename: Ferran
authors.initials: F
authors.lastname: Camp
authors.forename: Francesc
authors.initials: F
authors.lastname: Solanelles
authors.forename: Felip
authors.initials: F
authors.lastname: Gracia
authors.forename: Jordi
authors.initials: J
authors.lastname: Llorens
authors.forename: Emilio
authors.initials: E
authors.lastname: Gil
mesh_terms: D003198:Computer Simulation; D007753:Laboratories; D016014:Linear Models; D027845:Malus / Q000033:anatomy & histology*; D009716:Numerical Analysis, Computer-Assisted; D018515:Plant Leaves / Q000033:anatomy & histology*; D013016:Sound; D014197:Trees / Q000033:anatomy & histology*; D014465:Ultrasonics / Q000295:instrumentation*