On-the-Go Laser-based Sensing System for Measuring Plants Height Using an Autonomous Tractor

Abstract

Laser-based technologies are recently recognized for their impact on improving agricultural productivity and non-destructive measurement to the environment. The high temporal and low spatial resolutions have the limitations in implementing space and airborne aerial remote sensing methods for site specific management of crops. On the other hand, the ground-based sensing has immense potential for plant growth monitoring and becomes popular for site-specific management. Thus, the objectives of this research were to develop the operational scenario by an autonomous tractor and monitor plant growth based on the reflection height using laser range finders. In this regard, two Laser Range Finders (LRFs) were installed at the back of the autonomous tractor to conduct field experiments. First, LMS 211 LRF for relative positioning to approach the farm implement, coupling the implement and navigated at the field using artificial landmarks. Second, URG 04-LX LRF for quick assessment of crop status. The calibration of laser sensors was conducted for successful landmarks detection and plant canopy sensing. The autonomous tractor was used in this experiment with Programmable Logic Control (PLC) unit, hydraulic actuators for gear shifting and steering mechanism, LRF for relative positioning and RTK GPS for absolute positioning of the tractor. The operational scenario for field operations was developed including coupling, parking, and forward-backward movement using LMS211 LRF. The 2D laser cloud scan points were analyzed to measure reflection height from plants using URG 04-LX LRF. The reflection heights were used as a reference to develop surface map of plant growth under the tree canopy. Different types of plant’s reflection height were measured from the cluster of scan points reflected from the plant canopies at the Agricultural and Forest Research Center, University of Tsukuba. Further experiments will be presented to correlate plant growth and yield of plant biomass over the growing seasons.