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Multispectral Image Registration and Sensor Calibration for Low-Altitude Agricultural Drones
Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.ORCID iD: 0000-0001-9054-4746
Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.ORCID iD: 0000-0002-6834-5676
Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.ORCID iD: 0000-0003-3707-2780
Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.ORCID iD: 0000-0002-6643-312X
2024 (English)In: International Geoscience and Remote Sensing Symposium (IGARSS), Institute of Electrical and Electronics Engineers (IEEE), 2024, p. 6209-6213Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents a crucial multispectral image registration and sensor calibration method for an agricultural application. The multispectral images are obtained using a special drone equipped with multiple cameras flying at low altitudes. However, the distance between lenses, the lens distortions and the low-altitude flights lead to a lack of alignment in the built-in normalized difference vegetation index (NDVI). This lack of alignment results in a very poor performance in further analysis, especially for image segmentation and target detection to distinguish crops from invasive plants. In this work, we point out the importance of reducing this misalignment. To do so, the near-infrared and red sensors are first calibrated to remove the lens distortions. Then, the corresponding keypoints are utilized to calculate the transformation matrix and to minimize the back-projection error. The registered near-infrared and red images are then used to compute NDVI. The experimental results show higher alignment and F1-score of 0.73 which is a significant improvement in the performance of a trained deep neural network using NDVI in the detection of invasive plants. This is particularly a challenging task as the invasive plants resemble the desired crops.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2024. p. 6209-6213
Series
IEEE International Geoscience and Remote Sensing Symposium proceedings, ISSN 2153-6996, E-ISSN 2153-7003
Keywords [en]
Multispectral image registration, near-infrared image, normalized difference vegetation index (NDVI), sensor calibration, unmanned aerial vehicles, Aircraft detection, Drones, Image enhancement, Image registration, Image segmentation, Aerial vehicle, Images registration, Invasive plants, Multispectral images, Near- infrared images, Normalized difference vegetation index, Unmanned aerial vehicle, Deep neural networks
National Category
Computer graphics and computer vision
Identifiers
URN: urn:nbn:se:bth-27104DOI: 10.1109/IGARSS53475.2024.10642360ISI: 001415226901020Scopus ID: 2-s2.0-85208505152OAI: oai:DiVA.org:bth-27104DiVA, id: diva2:1913990
Conference
IEEE International Geoscience and Remote Sensing Symposium, IGARSS 2024, Athens, July 7-12, 2024
Available from: 2024-11-18 Created: 2024-11-18 Last updated: 2026-01-07Bibliographically approved
In thesis
1. AI-Driven Pattern Recognition and Object Detection: Emphasis on Precision Agriculture
Open this publication in new window or tab >>AI-Driven Pattern Recognition and Object Detection: Emphasis on Precision Agriculture
2025 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Precision agriculture utilizes Artificial Intelligence (AI) and remote sensing to address challenges in sustainable food production. A significant obstacle is effective weed management, particularly for species like black-grass (Alopecurus myosuroides), which visually resembles wheat. This thesis introduces AI-driven methods using Unmanned Aerial Vehicle (UAV)-based multispectral image analysis to improve weed detection, addressing key challenges such as limited datasets, sensor misalignment, and the need for robust algorithms.

The first part of the thesis addresses data scarcity using synthetic data augmentation. A study using a Mask Region-based Convolutional Neural Network (Mask R-CNN) model for black-grass detection shows that scaling foreground objects is a particularly effective technique for improving performance, providing a basis for adapting models to new field conditions with less data.

The second part focuses on multispectral data quality, where sensor misalignment can corrupt Vegetation Indices (VIs) like Normalized Difference Vegetation Index (NDVI). A method for sensor calibration and image registration is presented to correct for these errors. The study then evaluates various VIs, finding that models integrating indices like Triangular Greenness Index (TGI) and Excess Green Index (ExG) show improved detection performance compared to using only the basic spectral bands, particularly between crop rows.

Finally, the third part draws parallels to biometrics to explore the robustness of different network architectures. By evaluating triplet-based and Siamese networks for fingerprint recognition, it is demonstrated that clustering-based approaches using contrastive loss offer better performance with incomplete and variable data. This insight highlights broader principles for creating robust recognition systems.

Overall, this thesis contributes methods for addressing key obstacles in precision agriculture, spanning data augmentation, sensor calibration, and the optimization of deep learning models. The findings of this work aim to contribute to the ongoing development of more effective agricultural practices.

Place, publisher, year, edition, pages
Karlskrona: Blekinge Tekniska Högskola, 2025. p. 96
Series
Blekinge Institute of Technology Licentiate Dissertation Series, ISSN 1650-2140 ; 2025:10
Keywords
Precision agriculture, Weed detection, Deep learning, Object detection, Multispectral imaging, Vegetation indices, Unmanned Aerial Vehicles (UAVs), Synthetic data augmentation
National Category
Computer and Information Sciences Agriculture, Forestry and Fisheries Artificial Intelligence
Research subject
Systems Engineering
Identifiers
urn:nbn:se:bth-28605 (URN)978-91-7295-510-3 (ISBN)
Presentation
2025-10-08, C413A, Valhallavägen 10, Karlskrona, 10:00 (English)
Opponent
Supervisors
Note

Paper III is excluded from the attached file because of being submitted for publication in a journal.

Available from: 2025-09-11 Created: 2025-09-10 Last updated: 2025-09-30Bibliographically approved

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Hallösta, SimonJavadi, SalehDahl, MattiasPettersson, Mats

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