Method for Estimating Canopy Thickness Using Ultrasonic Sensor Technology

Huitao Zhou,Weidong Jia,Mingxiong Ou,Yong Li

doi:10.3390/agriculture11101011

Abstract

The accurate detection of canopy characteristics is the basis of precise variable spraying. Canopy characteristics such as canopy density, thickness and volume are needed to vary the pesticide application rate and adjust the spray flow rate and air supply volume. Canopy thickness is an important canopy dimension for the calculation of tree canopy volume in pesticide variable spraying. With regard to the phenomenon of ultrasonic waves with multiple reflections and the further analysis of echo signals, we found that there is a proportional relationship between the canopy thickness and echo interval time. In this paper, we propose a method to calculate canopy thickness using echo signals that come from ultrasonic sensors. To investigate the application of this method, we conducted a set of lab-based experiments with a simulated canopy. The results show that we can accurately estimate canopy thickness when the detection distance, canopy density, and canopy thickness range between 0.5and 1.5 m, 1.2 and 1.4, and 0.3and 0.6 m, respectively. The relative error between the estimated value and actual value of the simulated canopy thickness is no higher than 8.8%. To compare our lab results with trees in the field, we measured canopy thickness from three naturally occurring Osmanthus trees (Osmanthus fragrans Lour). The results showed that the mean relative errors of three Osmanthus trees are 19.2%, 19.4% and 18.8%, respectively. These results can be used to improve measurements for agricultural production that includes both orchards and facilities by providing a reference point for the precise application of variable spraying.

Highlights

Precise variable spraying is an effective method to reduce pesticide drift and excessive residues, which can achieve the on-demand spraying of pesticides based on canopy characteristics, including density, thickness, and volume
To verify the applicability and accuracy of canopy thickness detection methods in detecting real tree canopy information, outdoor experimental research on the detection of tree canopy thickness was carried out, and three Osmanthus trees with different canopy densities were selected for this experiment, which were recorded as tree A, tree B and tree
Ultrasonic echo signal data were acquired using a tree canopy canopy thickness was system calculated based on distances the canopy detection and the information detection at detection ofthickness

Summary

Introduction

Precise variable spraying is an effective method to reduce pesticide drift and excessive residues, which can achieve the on-demand spraying of pesticides based on canopy characteristics, including density, thickness, and volume. Precise variable spraying technology is an effective way to reduce pesticide waste and environmental pollution, which includes the automatic adjustment of the nozzle flow rate, the air supply volume, and the distance from nozzles to the tree according to the tree canopy characteristics [2,3,4]. With the canopy information detection method and system, real-time adjustments of the nozzle flow rate, spraying distance and other parameters are possible, which can effectively improve the utilization rate of pesticides and achieve the goal of reducing pesticides and increasing their effectiveness [6,7,8]

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Discussion

Conclusion