16,173 research outputs found
Mini-Unmanned Aerial Vehicle-Based Remote Sensing: Techniques, Applications, and Prospects
The past few decades have witnessed the great progress of unmanned aircraft
vehicles (UAVs) in civilian fields, especially in photogrammetry and remote
sensing. In contrast with the platforms of manned aircraft and satellite, the
UAV platform holds many promising characteristics: flexibility, efficiency,
high-spatial/temporal resolution, low cost, easy operation, etc., which make it
an effective complement to other remote-sensing platforms and a cost-effective
means for remote sensing. Considering the popularity and expansion of UAV-based
remote sensing in recent years, this paper provides a systematic survey on the
recent advances and future prospectives of UAVs in the remote-sensing
community. Specifically, the main challenges and key technologies of
remote-sensing data processing based on UAVs are discussed and summarized
firstly. Then, we provide an overview of the widespread applications of UAVs in
remote sensing. Finally, some prospects for future work are discussed. We hope
this paper will provide remote-sensing researchers an overall picture of recent
UAV-based remote sensing developments and help guide the further research on
this topic
Face Recognition in Low Quality Images: A Survey
Low-resolution face recognition (LRFR) has received increasing attention over
the past few years. Its applications lie widely in the real-world environment
when high-resolution or high-quality images are hard to capture. One of the
biggest demands for LRFR technologies is video surveillance. As the the number
of surveillance cameras in the city increases, the videos that captured will
need to be processed automatically. However, those videos or images are usually
captured with large standoffs, arbitrary illumination condition, and diverse
angles of view. Faces in these images are generally small in size. Several
studies addressed this problem employed techniques like super resolution,
deblurring, or learning a relationship between different resolution domains. In
this paper, we provide a comprehensive review of approaches to low-resolution
face recognition in the past five years. First, a general problem definition is
given. Later, systematically analysis of the works on this topic is presented
by catogory. In addition to describing the methods, we also focus on datasets
and experiment settings. We further address the related works on unconstrained
low-resolution face recognition and compare them with the result that use
synthetic low-resolution data. Finally, we summarized the general limitations
and speculate a priorities for the future effort.Comment: There are some mistakes addressing in this paper which will be
misleading to the reader and we wont have a new version in short time. We
will resubmit once it is being corecte
Dense Haze: A benchmark for image dehazing with dense-haze and haze-free images
Single image dehazing is an ill-posed problem that has recently drawn
important attention. Despite the significant increase in interest shown for
dehazing over the past few years, the validation of the dehazing methods
remains largely unsatisfactory, due to the lack of pairs of real hazy and
corresponding haze-free reference images. To address this limitation, we
introduce Dense-Haze - a novel dehazing dataset. Characterized by dense and
homogeneous hazy scenes, Dense-Haze contains 33 pairs of real hazy and
corresponding haze-free images of various outdoor scenes. The hazy scenes have
been recorded by introducing real haze, generated by professional haze
machines. The hazy and haze-free corresponding scenes contain the same visual
content captured under the same illumination parameters. Dense-Haze dataset
aims to push significantly the state-of-the-art in single-image dehazing by
promoting robust methods for real and various hazy scenes. We also provide a
comprehensive qualitative and quantitative evaluation of state-of-the-art
single image dehazing techniques based on the Dense-Haze dataset. Not
surprisingly, our study reveals that the existing dehazing techniques perform
poorly for dense homogeneous hazy scenes and that there is still much room for
improvement.Comment: 5 pages, 2 figure
Real-world Underwater Enhancement: Challenges, Benchmarks, and Solutions
Underwater image enhancement is such an important low-level vision task with
many applications that numerous algorithms have been proposed in recent years.
These algorithms developed upon various assumptions demonstrate successes from
various aspects using different data sets and different metrics. In this work,
we setup an undersea image capturing system, and construct a large-scale
Real-world Underwater Image Enhancement (RUIE) data set divided into three
subsets. The three subsets target at three challenging aspects for enhancement,
i.e., image visibility quality, color casts, and higher-level
detection/classification, respectively. We conduct extensive and systematic
experiments on RUIE to evaluate the effectiveness and limitations of various
algorithms to enhance visibility and correct color casts on images with
hierarchical categories of degradation. Moreover, underwater image enhancement
in practice usually serves as a preprocessing step for mid-level and high-level
vision tasks. We thus exploit the object detection performance on enhanced
images as a brand new task-specific evaluation criterion. The findings from
these evaluations not only confirm what is commonly believed, but also suggest
promising solutions and new directions for visibility enhancement, color
correction, and object detection on real-world underwater images.Comment: arXiv admin note: text overlap with arXiv:1712.04143 by other author
Benchmarking Single Image Dehazing and Beyond
We present a comprehensive study and evaluation of existing single image
dehazing algorithms, using a new large-scale benchmark consisting of both
synthetic and real-world hazy images, called REalistic Single Image DEhazing
(RESIDE). RESIDE highlights diverse data sources and image contents, and is
divided into five subsets, each serving different training or evaluation
purposes. We further provide a rich variety of criteria for dehazing algorithm
evaluation, ranging from full-reference metrics, to no-reference metrics, to
subjective evaluation and the novel task-driven evaluation. Experiments on
RESIDE shed light on the comparisons and limitations of state-of-the-art
dehazing algorithms, and suggest promising future directions.Comment: IEEE Transactions on Image Processing(TIP 2019
An All-in-One Network for Dehazing and Beyond
This paper proposes an image dehazing model built with a convolutional neural
network (CNN), called All-in-One Dehazing Network (AOD-Net). It is designed
based on a re-formulated atmospheric scattering model. Instead of estimating
the transmission matrix and the atmospheric light separately as most previous
models did, AOD-Net directly generates the clean image through a light-weight
CNN. Such a novel end-to-end design makes it easy to embed AOD-Net into other
deep models, e.g., Faster R-CNN, for improving high-level task performance on
hazy images. Experimental results on both synthesized and natural hazy image
datasets demonstrate our superior performance than the state-of-the-art in
terms of PSNR, SSIM and the subjective visual quality. Furthermore, when
concatenating AOD-Net with Faster R-CNN and training the joint pipeline from
end to end, we witness a large improvement of the object detection performance
on hazy images
Convolutional Sparse Coding for Compressed Sensing CT Reconstruction
Over the past few years, dictionary learning (DL)-based methods have been
successfully used in various image reconstruction problems. However,
traditional DL-based computed tomography (CT) reconstruction methods are
patch-based and ignore the consistency of pixels in overlapped patches. In
addition, the features learned by these methods always contain shifted versions
of the same features. In recent years, convolutional sparse coding (CSC) has
been developed to address these problems. In this paper, inspired by several
successful applications of CSC in the field of signal processing, we explore
the potential of CSC in sparse-view CT reconstruction. By directly working on
the whole image, without the necessity of dividing the image into overlapped
patches in DL-based methods, the proposed methods can maintain more details and
avoid artifacts caused by patch aggregation. With predetermined filters, an
alternating scheme is developed to optimize the objective function. Extensive
experiments with simulated and real CT data were performed to validate the
effectiveness of the proposed methods. Qualitative and quantitative results
demonstrate that the proposed methods achieve better performance than several
existing state-of-the-art methods.Comment: Accepted by IEEE TM
Bridging the Gap Between Computational Photography and Visual Recognition
What is the current state-of-the-art for image restoration and enhancement
applied to degraded images acquired under less than ideal circumstances? Can
the application of such algorithms as a pre-processing step to improve image
interpretability for manual analysis or automatic visual recognition to
classify scene content? While there have been important advances in the area of
computational photography to restore or enhance the visual quality of an image,
the capabilities of such techniques have not always translated in a useful way
to visual recognition tasks. Consequently, there is a pressing need for the
development of algorithms that are designed for the joint problem of improving
visual appearance and recognition, which will be an enabling factor for the
deployment of visual recognition tools in many real-world scenarios. To address
this, we introduce the UG^2 dataset as a large-scale benchmark composed of
video imagery captured under challenging conditions, and two enhancement tasks
designed to test algorithmic impact on visual quality and automatic object
recognition. Furthermore, we propose a set of metrics to evaluate the joint
improvement of such tasks as well as individual algorithmic advances, including
a novel psychophysics-based evaluation regime for human assessment and a
realistic set of quantitative measures for object recognition performance. We
introduce six new algorithms for image restoration or enhancement, which were
created as part of the IARPA sponsored UG^2 Challenge workshop held at CVPR
2018. Under the proposed evaluation regime, we present an in-depth analysis of
these algorithms and a host of deep learning-based and classic baseline
approaches. From the observed results, it is evident that we are in the early
days of building a bridge between computational photography and visual
recognition, leaving many opportunities for innovation in this area.Comment: CVPR Prize Challenge: http://www.ug2challenge.or
Does Haze Removal Help CNN-based Image Classification?
Hazy images are common in real scenarios and many dehazing methods have been
developed to automatically remove the haze from images. Typically, the goal of
image dehazing is to produce clearer images from which human vision can better
identify the object and structural details present in the images. When the
ground-truth haze-free image is available for a hazy image, quantitative
evaluation of image dehazing is usually based on objective metrics, such as
Peak Signal-to-Noise Ratio (PSNR) and Structural Similarity (SSIM). However, in
many applications, large-scale images are collected not for visual examination
by human. Instead, they are used for many high-level vision tasks, such as
automatic classification, recognition and categorization. One fundamental
problem here is whether various dehazing methods can produce clearer images
that can help improve the performance of the high-level tasks. In this paper,
we empirically study this problem in the important task of image classification
by using both synthetic and real hazy image datasets. From the experimental
results, we find that the existing image-dehazing methods cannot improve much
the image-classification performance and sometimes even reduce the
image-classification performance
Automatic Region-wise Spatially Varying Coefficient Regression Model: an Application to National Cardiovascular Disease Mortality and Air Pollution Association Study
Motivated by analyzing a national data base of annual air pollution and
cardiovascular disease mortality rate for 3100 counties in the U.S. (areal
data), we develop a novel statistical framework to automatically detect
spatially varying region-wise associations between air pollution exposures and
health outcomes. The automatic region-wise spatially varying coefficient model
consists three parts: we first compute the similarity matrix between the
exposure-health outcome associations of all spatial units, then segment the
whole map into a set of disjoint regions based on the adjacency matrix with
constraints that all spatial units within a region are contiguous and have
similar association, and lastly estimate the region specific associations
between exposure and health outcome. We implement the framework by using
regression and spectral graph techniques. We develop goodness of fit criteria
for model assessment and model selection. The simulation study confirms the
satisfactory performance of our model. We further employ our method to
investigate the association between airborne particulate matter smaller than
2.5 microns (PM 2.5) and cardiovascular disease mortality. The results
successfully identify regions with distinct associations between the mortality
rate and PM 2.5 that may provide insightful guidance for environmental health
research
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