A Method to Obtain Orange Crop Geometry Information Using a Mobile Terrestrial Laser Scanner and 3D Modeling

André Colaço,José Molin,Joan Rosell-Polo,Alexandre Escolà,Rodrigo Trevisan

doi:10.3390/rs9080763

André Colaço, José Molin + Show 3 more

Open Access

https://doi.org/10.3390/rs9080763

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Journal: Remote sensing	Publication Date: Jul 25, 2017
Citations: 64	License type: CC BY 4.0

Affiliation: Universidade de São Paulo, University of Lleida

Abstract

LiDAR (Light Detection and Ranging) technology has been used to obtain geometrical attributes of tree crops in small field plots, sometimes using manual steps in data processing. The objective of this study was to develop a method for estimating canopy volume and height based on a mobile terrestrial laser scanner suited for large commercial orange groves. A 2D LiDAR sensor and a GNSS (Global Navigation Satellite System) receiver were mounted on a vehicle for data acquisition. A georeferenced point cloud representing the laser beam impacts on the crop was created and later classified into transversal sections along the row or into individual trees. The convex-hull and the alpha-shape reconstruction algorithms were used to reproduce the shape of the tree crowns. Maps of canopy volume and height were generated for a 25 ha orange grove. The different options of data processing resulted in different values of canopy volume. The alpha-shape algorithm was considered a good option to represent individual trees whereas the convex-hull was better when representing transversal sections of the row. Nevertheless, the canopy volume and height maps produced by those two methods were similar. The proposed system is useful for site-specific management in orange groves.

Highlights

The 3D modeling of canopies has become an important research topic in precision agriculture, especially in tree crops—see reviews by Dworak et al [1], Rosell-Polo and Sanz [2], Berk et al [3] andGil et al [4]
The accuracy of the point cloud derived from the mobile terrestrial laser scanners” (MTLS) was assessed by using regular objects as targets for scanning
A methodology for 3D modeling and canopy geometry computation for orange groves was developed using a mobile terrestrial laser scanning system based on a LiDAR sensor

Summary

Introduction

The 3D modeling of canopies has become an important research topic in precision agriculture, especially in tree crops—see reviews by Dworak et al [1], Rosell-Polo and Sanz [2], Berk et al [3] and. Gil et al [4]. This technique seeks to provide accurate information about canopy dimensions and foliage density, which relates to plant development and health. Ground-based LiDAR (Light Detection and Ranging) scanning has proven to be a viable option for modeling geometrical features of tree crops [2,5,6,7]. By estimating the distance between its centre and the nearest obstacle in several directions (if a 2D or 3D sensor is used), a LiDAR sensor can be used to create 3D models of its surroundings. An advantage of terrestrial acquisition systems in the context of agricultural and horticultural applications is that the sensors can be attached to spreaders and spraying machines enabling variable-rate applications on a real-time basis [8,9], thereby not requiring an extra operation to acquire data from orchards or groves; these are often referred to as “mobile terrestrial laser scanners” (MTLS) [7,10,11,12,13].

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