Journal ArticleDOI
Different colours of shadows: classification of UAV images
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In this study, the Maximum Likelihood (ML) and Support Vector Machine (SVM) classifiers were used to classify a UAV image acquired using a red–green–blue (RGB) camera over the Old Woman Creek National Estuarine Research Reserve in Ohio, USA.Abstract:
Due to their low light conditions, shadows reduce the accuracy of feature extraction and change detection in remote-sensing images. Unmanned aerial vehicles UAVs are capable of acquiring images that have a resolution of several centimetres and removing shadows is a challenge. In this study, the Maximum Likelihood ML and Support Vector Machine SVM classifiers were used to classify a UAV image acquired using a red–green–blue RGB camera over the Old Woman Creek National Estuarine Research Reserve in Ohio, USA. The impact of shadows on the classification process was explored for different pixel sizes ranging from 0.03 to 1.00 m. The SVM generated higher overall accuracy OA at finer spatial resolution 0.25–0.50 m, while the optimal spatial resolution for the ML classifier was 1.00 m. The percentage of shadow coverage increased with spatial resolution for both classifiers 1.71% for ML and 6.63% for SVM. Shadows were detected and extracted using two approaches: a as a separate class using regions of interests ROIs observed in the image, and b by applying a segmentation threshold of 0.3 to visible atmospherically resistant index VARI. The extracted shadows were separately classified using ROIs selected from shaded surfaces, and then removed using the fusion of RGB reflectance, VARI, and digital surface model DSM images. The OA of classified shadows reached 91.50%. OAs of merged sunlit and shadow classified images improved for 18.48% for SVM, and 17.62% for the ML classifier. VARI accurately captures shadows, and when fused with RGB reflectance and DSM, it intensifies their low signal and enhances classification. Whether used to capture or to remove shadows, VARI serves as an effective ‘shadow index’. Shadows create obstacles to remote-sensing processing; however, their spectral information should not be neglected as both shadows and sunlit areas are important for ecological processes such as photosynthesis, carbon balance, evapotranspiration, fish abundance, and more.read more
Citations
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Journal ArticleDOI
Convolutional Neural Networks enable efficient, accurate and fine-grained segmentation of plant species and communities from high-resolution UAV imagery
TL;DR: This work demonstrates that a CNN-based segmentation approach (U-net) in combination with training data directly derived from visual interpretation of UAV-based high-resolution RGB imagery for fine-grained mapping of vegetation species and communities and suggests that plant identification at very high spatial resolutions is facilitated through spatial patterns rather than spectral information.
Journal ArticleDOI
Comparison of ALS- and UAV(SfM)-derived high-density point clouds for individual tree detection in Eucalyptus plantations
Juan Guerra-Hernández,Diogo Nepomuceno Cosenza,Luiz Carlos Estraviz Rodriguez,Margarida Silva,Margarida Tomé,Ramón Alberto Díaz-Varela,Eduardo González-Ferreiro,Eduardo González-Ferreiro +7 more
TL;DR: In this paper, high accurate, rapid forest inventory techniques are needed to enable forest managers to address the increasing demand for sustainable forestry, which can be achieved by using Airborne Laser Scanning (ALS).
Journal ArticleDOI
Identifying and mapping individual plants in a highly diverse high-elevation ecosystem using UAV imagery and deep learning
TL;DR: Results demonstrate that the SS Res U-Net has the ability to self-adapt to variation in objects, and consistently achieved the highest classification accuracy compared with four state of the art benchmark approaches.
Journal ArticleDOI
UFCN: a fully convolutional neural network for road extraction in RGB imagery acquired by remote sensing from an unmanned aerial vehicle
Ramesh Kestur,Shariq Farooq,Rameen Abdal,Emad Mehraj,Omkar Subbaramajois Narasipura,Meenavathi Mudigere +5 more
TL;DR: The proposed UFCN (U-shaped FCN) is an FCN architecture, which is comprised of a stack of convolutions followed by corresponding stack of mirrored deconvolutions with the usage of skip connections in between for preserving the local information.
Journal ArticleDOI
How canopy shadow affects invasive plant species classification in high spatial resolution remote sensing
TL;DR: In this paper, the effect of shadows on mapping the occurrence of invasive species using UAV-based data was studied, and it was shown that shadows significantly affect the accuracies obtained with all types of variables.
References
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Journal ArticleDOI
Support vector machines in remote sensing: A review
TL;DR: This paper reviews remote sensing implementations of support vector machines (SVMs), a promising machine learning methodology that is particularly appealing in the remote sensing field due to their ability to generalize well even with limited training samples.
Journal ArticleDOI
Novel algorithms for remote estimation of vegetation fraction
TL;DR: In this article, the information content of reflectance spectra in visible range can be expressed by only two independent pairs of spectral bands: (1) the blue from 400 to 500 nm and the red near 670 nm; (2) the green around 550 nm; and (3) the red edge region near 700 nm.
Journal ArticleDOI
Atmospherically resistant vegetation index (ARVI) for EOS-MODIS
Yoram J. Kaufman,Didier Tanré +1 more
TL;DR: Simulations using radiative transfer computations on arithmetic and natural surface spectra, for various atmospheric conditions, show that ARVI has a similar dynamic range to the NDVI, but is, on average, four times less sensitive to atmospheric effects than theNDVI.
Book
Computer Processing of Remotely-Sensed Images
TL;DR: Computer processing of remote-sensed images, Computer processing of remotely-sensing images, and so on.
Journal ArticleDOI
Geometric-Optical Modeling of a Conifer Forest Canopy
Xiaowen Li,Alan H. Strahler +1 more
TL;DR: In this paper, a geometric-optical forest canopy model that treats conifers as cones casting shadows on a contrasting background is proposed to explain the major portion of the variance in a remotely sensed image of a forest stand.