9 research outputs found
A Non-Local Structure Tensor Based Approach for Multicomponent Image Recovery Problems
Non-Local Total Variation (NLTV) has emerged as a useful tool in variational
methods for image recovery problems. In this paper, we extend the NLTV-based
regularization to multicomponent images by taking advantage of the Structure
Tensor (ST) resulting from the gradient of a multicomponent image. The proposed
approach allows us to penalize the non-local variations, jointly for the
different components, through various matrix norms with .
To facilitate the choice of the hyper-parameters, we adopt a constrained convex
optimization approach in which we minimize the data fidelity term subject to a
constraint involving the ST-NLTV regularization. The resulting convex
optimization problem is solved with a novel epigraphical projection method.
This formulation can be efficiently implemented thanks to the flexibility
offered by recent primal-dual proximal algorithms. Experiments are carried out
for multispectral and hyperspectral images. The results demonstrate the
interest of introducing a non-local structure tensor regularization and show
that the proposed approach leads to significant improvements in terms of
convergence speed over current state-of-the-art methods
Thick Cloud Removal of Remote Sensing Images Using Temporal Smoothness and Sparsity-Regularized Tensor Optimization
In remote sensing images, the presence of thick cloud accompanying cloud
shadow is a high probability event, which can affect the quality of subsequent
processing and limit the scenarios of application. Hence, removing the thick
cloud and cloud shadow as well as recovering the cloud-contaminated pixels is
indispensable to make good use of remote sensing images. In this paper, a novel
thick cloud removal method for remote sensing images based on temporal
smoothness and sparsity-regularized tensor optimization (TSSTO) is proposed.
The basic idea of TSSTO is that the thick cloud and cloud shadow are not only
sparse but also smooth along the horizontal and vertical direction in images
while the clean images are smooth along the temporal direction between images.
Therefore, the sparsity norm is used to boost the sparsity of the cloud and
cloud shadow, and unidirectional total variation (UTV) regularizers are applied
to ensure the unidirectional smoothness. This paper utilizes alternation
direction method of multipliers to solve the presented model and generate the
cloud and cloud shadow element as well as the clean element. The cloud and
cloud shadow element is purified to get the cloud area and cloud shadow area.
Then, the clean area of the original cloud-contaminated images is replaced to
the corresponding area of the clean element. Finally, the reference image is
selected to reconstruct details of the cloud area and cloud shadow area using
the information cloning method. A series of experiments are conducted both on
simulated and real cloud-contaminated images from different sensors and with
different resolutions, and the results demonstrate the potential of the
proposed TSSTO method for removing cloud and cloud shadow from both qualitative
and quantitative viewpoints
Non-local tensor completion for multitemporal remotely sensed images inpainting
Remotely sensed images may contain some missing areas because of poor weather
conditions and sensor failure. Information of those areas may play an important
role in the interpretation of multitemporal remotely sensed data. The paper
aims at reconstructing the missing information by a non-local low-rank tensor
completion method (NL-LRTC). First, nonlocal correlations in the spatial domain
are taken into account by searching and grouping similar image patches in a
large search window. Then low-rankness of the identified 4-order tensor groups
is promoted to consider their correlations in spatial, spectral, and temporal
domains, while reconstructing the underlying patterns. Experimental results on
simulated and real data demonstrate that the proposed method is effective both
qualitatively and quantitatively. In addition, the proposed method is
computationally efficient compared to other patch based methods such as the
recent proposed PM-MTGSR method
Cloud Removal in Sentinel-2 Imagery using a Deep Residual Neural Network and SAR-Optical Data Fusion
Optical remote sensing imagery is at the core of many Earth observation activities. The regular, consistent and global-scale nature of the satellite data is exploited in many applications, such as cropland monitoring, climate change assessment, land-cover and land-use classification, and disaster assessment. However, one main problem severely affects the temporal and spatial availability of surface observations, namely cloud cover. The task of removing clouds from optical images has been subject of studies since decades. The advent of the Big Data era in satellite remote sensing opens new possibilities for tackling the problem using powerful data-driven deep learning methods. In this paper, a deep residual neural network architecture is designed to remove clouds from multispectral Sentinel-2 imagery. SAR-optical data fusion is used to exploit the synergistic properties of the two imaging systems to guide the image reconstruction. Additionally, a novel cloud-adaptive loss is proposed to maximize the retainment of original information. The network is trained and tested on a globally sampled dataset comprising real cloudy and cloud-free images. The proposed setup allows to remove even optically thick clouds by reconstructing an optical representation of the underlying land surface structure
Multi-feature combined cloud and cloud shadow detection in GaoFen-1 wide field of view imagery
The wide field of view (WFV) imaging system onboard the Chinese GaoFen-1
(GF-1) optical satellite has a 16-m resolution and four-day revisit cycle for
large-scale Earth observation. The advantages of the high temporal-spatial
resolution and the wide field of view make the GF-1 WFV imagery very popular.
However, cloud cover is an inevitable problem in GF-1 WFV imagery, which
influences its precise application. Accurate cloud and cloud shadow detection
in GF-1 WFV imagery is quite difficult due to the fact that there are only
three visible bands and one near-infrared band. In this paper, an automatic
multi-feature combined (MFC) method is proposed for cloud and cloud shadow
detection in GF-1 WFV imagery. The MFC algorithm first implements threshold
segmentation based on the spectral features and mask refinement based on guided
filtering to generate a preliminary cloud mask. The geometric features are then
used in combination with the texture features to improve the cloud detection
results and produce the final cloud mask. Finally, the cloud shadow mask can be
acquired by means of the cloud and shadow matching and follow-up correction
process. The method was validated using 108 globally distributed scenes. The
results indicate that MFC performs well under most conditions, and the average
overall accuracy of MFC cloud detection is as high as 96.8%. In the contrastive
analysis with the official provided cloud fractions, MFC shows a significant
improvement in cloud fraction estimation, and achieves a high accuracy for the
cloud and cloud shadow detection in the GF-1 WFV imagery with fewer spectral
bands. The proposed method could be used as a preprocessing step in the future
to monitor land-cover change, and it could also be easily extended to other
optical satellite imagery which has a similar spectral setting.Comment: This manuscript has been accepted for publication in Remote Sensing
of Environment, vol. 191, pp.342-358, 2017.
(http://www.sciencedirect.com/science/article/pii/S003442571730038X
Detección automática, clasificación y reconocimiento de escorpiones mediante técnicas de Aprendizaje Profundo
La detección e identificación temprana de los escorpiones es esencial debido a la peligrosidad de estos arácnidos que ponen en riesgo la salud de la población, en particular, de los sectores más vulnerables al veneno de un escorpión, como son las personas hipertensas, cardÃacas o diabéticas, pero también los niños y los ancianos. A su vez, la detección y clasificación de escorpiones puede ser útil con fines de investigación biológica para estudiar las diferentes variedades de géneros y especies. En este trabajo, con el propósito de brindar herramientas de prevención alternativas, se desarrollaron novedosos sistemas automáticos y en tiempo real para detectar y clasificar escorpiones, utilizando heurÃsticas de visión artificial y Aprendizaje Profundo, basados en las caracterÃsticas de la forma y la propiedad de fluorescencia de los escorpiones cuando son expuesto a luz ultravioleta. En particular, se han investigado las tres especies de escorpiones que se encuentran en la ciudad de La Plata: Bothriurus bonariensis (sin importancia sanitaria), Tityus carrilloi y Tityus confluens (ambas de importancia sanitaria). Durante este trabajo se llevaron a cabo comparaciones entre diferentes modelos basados en Aprendizaje Profundo utilizados para detectar e identificar escorpiones, ya sea por género peligroso o no peligroso, como para determinar su especie dentro de un mismo género. Los resultados satisfactorios obtenidos indican que los sistemas desarrollados pueden, de forma temprana, precisa, no invasiva y segura, detectar y clasificar escorpiones, incluso dentro de un ambiente no controlado, es decir, cuando el escorpión se encuentra cerca de otros objetos que podrÃan dificultar su detección. Los sistemas de detección y clasificación desarrollados en este trabajo se implementaron como una aplicación móvil, con la ventaja de la portabilidad y la facilidad de acceso a la población, que puede ser utilizada como una herramienta de prevención eficaz para minimizar las picaduras de escorpiones y ayudar a reducir el daño que pueden ocasionar a las poblaciones expuestas a estos arácnidos. Además, estos sistemas son fácilmente escalables a otros géneros y especies de escorpiones para ampliar la región donde se puedan utilizar estas aplicaciones.Facultad de IngenierÃ