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Article

Individual Palm Tree Detection Using Deep Learning on RGB Imagery to Support Tree Inventory

1
Flemish Institute for Technological Research-VITO NV, Boeretang 200, 2400 Mol, Belgium
2
Division of Forest, Nature and Landscape, KU Leuven, 3001 Leuven, Belgium
*
Author to whom correspondence should be addressed.
Remote Sens. 2020, 12(21), 3476; https://doi.org/10.3390/rs12213476
Received: 28 August 2020 / Revised: 29 September 2020 / Accepted: 16 October 2020 / Published: 22 October 2020
(This article belongs to the Special Issue Deep Neural Networks for Remote Sensing Applications)
Phoenix palms cover more than 1.3 million hectares in the Mediterranean, Middle East, and North Africa regions and they represent highly valued assets for economic, environmental, and cultural purposes. Despite their importance, information on the number of palm trees and the palm distribution across different scenes is difficult to obtain and, therefore, limited. In this work, we present the first region-wide spatial inventory of Phoenix dactylifera (date palm) and Phoenix canariensis (canary palm) trees, based on remote imagery from the Alicante province in Spain. A deep learning architecture that was based on convolutional neural networks (CNN) was implemented to generate a detection model able to locate and classify individual palms trees from aerial high-resolution RGB images. When considering that creating large labeled image datasets is a constraint in object detection applied to remote sensing data, as a strategy for pre-training detection models on a similar task, imagery and palm maps from the autonomous community of the Canary Islands were used. Subsequently, these models were transferred for re-training with imagery from Alicante. The best performing model was capable of mapping Phoenix palms in different scenes, with a changeable appearance, and with varied ages, achieving a mean average precision (mAP) value of 0.861. In total, 511,095 Phoenix palms with a probability score above 0.5 were detected over an area of 5816 km2. The detection model, which was obtained from an out-of-the-box object detector, RetinaNet, provides a fast and straightforward method to map isolated and densely distributed date and canary palms—and other Phoenix palms. The inventory of palm trees established here provides quantitative information on Phoenix palms distribution, which could be used as a baseline for long-term monitoring of palms’ conditions. In addition to boosting palm tree inventory across multiple landscapes at a large scale, the detection model demonstrates how image processing techniques that are based on deep learning leverage image understanding from remote sensing data. View Full-Text
Keywords: aerial images; machine learning; object detection; tree inventory; palm trees; convolutional neural networks; large scale; environmental mapping aerial images; machine learning; object detection; tree inventory; palm trees; convolutional neural networks; large scale; environmental mapping
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MDPI and ACS Style

Culman, M.; Delalieux, S.; Van Tricht, K. Individual Palm Tree Detection Using Deep Learning on RGB Imagery to Support Tree Inventory. Remote Sens. 2020, 12, 3476. https://doi.org/10.3390/rs12213476

AMA Style

Culman M, Delalieux S, Van Tricht K. Individual Palm Tree Detection Using Deep Learning on RGB Imagery to Support Tree Inventory. Remote Sensing. 2020; 12(21):3476. https://doi.org/10.3390/rs12213476

Chicago/Turabian Style

Culman, María, Stephanie Delalieux, and Kristof Van Tricht. 2020. "Individual Palm Tree Detection Using Deep Learning on RGB Imagery to Support Tree Inventory" Remote Sensing 12, no. 21: 3476. https://doi.org/10.3390/rs12213476

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