305 research outputs found
SPARSE POINT CLOUD FILTERING BASED ON COVARIANCE FEATURES
Abstract. This work presents an extended photogrammetric pipeline aimed to improve 3D reconstruction results. Standard photogrammetric pipelines can produce noisy 3D data, especially when images are acquired with various sensors featuring different properties. In this paper, we propose an automatic filtering procedure based on some geometric features computed on the sparse point cloud created within the bundle adjustment phase. Bad 3D tie points and outliers are detected and removed, relying on micro and macro-clusters analyses. Clusters are built according to the prevalent dimensionality class (1D, 2D, 3D) assigned to low-entropy points, and corresponding to the main linear, planar o scatter local behaviour of the point cloud. While the macro-clusters analysis removes smallsized clusters and high-entropy points, in the micro-clusters investigation covariance features are used to verify the inner coherence of each point to the assigned class. Results on heritage scenarios are presented and discussed.</p
Image-based Recommendations on Styles and Substitutes
Humans inevitably develop a sense of the relationships between objects, some
of which are based on their appearance. Some pairs of objects might be seen as
being alternatives to each other (such as two pairs of jeans), while others may
be seen as being complementary (such as a pair of jeans and a matching shirt).
This information guides many of the choices that people make, from buying
clothes to their interactions with each other. We seek here to model this human
sense of the relationships between objects based on their appearance. Our
approach is not based on fine-grained modeling of user annotations but rather
on capturing the largest dataset possible and developing a scalable method for
uncovering human notions of the visual relationships within. We cast this as a
network inference problem defined on graphs of related images, and provide a
large-scale dataset for the training and evaluation of the same. The system we
develop is capable of recommending which clothes and accessories will go well
together (and which will not), amongst a host of other applications.Comment: 11 pages, 10 figures, SIGIR 201
Optimal Window and Lattice in Gabor Transform Application to Audio Analysis
This article deals with the use of optimal lattice and optimal window in
Discrete Gabor Transform computation. In the case of a generalized Gaussian
window, extending earlier contributions, we introduce an additional local
window adaptation technique for non-stationary signals. We illustrate our
approach and the earlier one by addressing three time-frequency analysis
problems to show the improvements achieved by the use of optimal lattice and
window: close frequencies distinction, frequency estimation and SNR estimation.
The results are presented, when possible, with real world audio signals
Deep-Learning for Classification of Colorectal Polyps on Whole-Slide Images
Histopathological characterization of colorectal polyps is an important
principle for determining the risk of colorectal cancer and future rates of
surveillance for patients. This characterization is time-intensive, requires
years of specialized training, and suffers from significant inter-observer and
intra-observer variability. In this work, we built an automatic
image-understanding method that can accurately classify different types of
colorectal polyps in whole-slide histology images to help pathologists with
histopathological characterization and diagnosis of colorectal polyps. The
proposed image-understanding method is based on deep-learning techniques, which
rely on numerous levels of abstraction for data representation and have shown
state-of-the-art results for various image analysis tasks. Our
image-understanding method covers all five polyp types (hyperplastic polyp,
sessile serrated polyp, traditional serrated adenoma, tubular adenoma, and
tubulovillous/villous adenoma) that are included in the US multi-society task
force guidelines for colorectal cancer risk assessment and surveillance, and
encompasses the most common occurrences of colorectal polyps. Our evaluation on
239 independent test samples shows our proposed method can identify the types
of colorectal polyps in whole-slide images with a high efficacy (accuracy:
93.0%, precision: 89.7%, recall: 88.3%, F1 score: 88.8%). The presented method
in this paper can reduce the cognitive burden on pathologists and improve their
accuracy and efficiency in histopathological characterization of colorectal
polyps, and in subsequent risk assessment and follow-up recommendations
Geometric feature analysis for the classification of cultural heritage point clouds
In the last years, the application of artificial intelligence (Machine Learning and Deep Learning methods) for the classification of 3D point clouds has become an important task in modern 3D documentation and modelling applications. The identification of proper geometric and radiometric features becomes fundamental to classify 2D/3D data correctly. While many studies have been conducted in the geospatial field, the cultural heritage sector is still partly unexplored. In this paper we analyse the efficacy of the geometric covariance features as a support for the classification of Cultural Heritage point clouds. To analyse the impact of the different features calculated on spherical neighbourhoods at various radius sizes, we present results obtained on four different heritage case studies using different features configurations
Generalized Many-Way Few-Shot Video Classification
Few-shot learning methods operate in low data regimes. The aim is to learn with few training examples per class. Although significant progress has been made in few-shot image classification, few-shot video recognition is relatively unexplored and methods based on 2D CNNs are unable to learn temporal information. In this work we thus develop a simple 3D CNN baseline, surpassing existing methods by a large margin. To circumvent the need of labeled examples, we propose to leverage weakly-labeled videos from a large dataset using tag retrieval followed by selecting the best clips with visual similarities, yielding further improvement. Our results saturate current 5-way benchmarks for few-shot video classification and therefore we propose a new challenging benchmark involving more classes and a mixture of classes with varying supervision
On-Off Intermittency in Time Series of Spontaneous Paroxysmal Activity in Rats with Genetic Absence Epilepsy
Dynamic behavior of complex neuronal ensembles is a topic comprising a
streamline of current researches worldwide. In this article we study the
behavior manifested by epileptic brain, in the case of spontaneous
non-convulsive paroxysmal activity. For this purpose we analyzed archived
long-term recording of paroxysmal activity in animals genetically susceptible
to absence epilepsy, namely WAG/Rij rats. We first report that the brain
activity alternated between normal states and epilepsy paroxysms is the on-off
intermittency phenomenon which has been observed and studied earlier in the
different nonlinear systems.Comment: 11 pages, 6 figure
Time-lapsing biodiversity: an open source method for measuring diversity changes by remote sensing
Understanding biodiversity changes in time is crucial to promptly provide management practices against diversity loss. This is overall true when considering global scales, since human-induced global change is expected to make significant changes on the Earth's biota. Biodiversity management and planning is mainly based on field observations related to community diversity, considering different taxa. However, such methods are time and cost demanding and do not allow in most cases to get temporal replicates. In this view, remote sensing can provide a wide data coverage in a short period of time. Recently, the use of Rao's Q diversity as a measure of spectral diversity has been proposed in order to explicitly take into account differences in a neighbourhood considering abundance and relative distance among pixels. The aim of this paper was to extend such a measure over the temporal dimension and to present an innovative approach to calculate remotely sensed temporal diversity. We demonstrated that temporal beta-diversity (spectral turnover) can be calculated pixel-wise in terms of both slope and coefficient of variation and further plotted over the whole matrix / image. From an ecological and operational point of view, for prioritisation practices in biodiversity protection, temporal variability could be beneficial in order to plan more efficient conservation practices starting from spectral diversity hotspots in space and time. In this paper, we delivered a highly reproducible approach to calculate spatio-temporal diversity in a robust and straightforward manner. Since it is based on open source code, we expect that our method will be further used by several researchers and landscape managers
QUALITY FEATURES FOR THE INTEGRATION OF TERRESTRIAL AND UAV IMAGES
The paper presents an innovative approach for improving the orientation results when terrestrial and UAV images are jointly processed. With the existing approaches, the processing of images coming from different platforms and sensors leads often to noisy and inaccurate 3D reconstructions, due to the different nature and properties of the acquired images. In this work, a photogrammetric pipeline is proposed to filter and remove bad computed tie points, according to some quality feature indicators. A completely automatic procedure has been developed to filter the sparse point cloud, in order to improve the orientation results before computing the dense point cloud. We report some tests and results on a dataset of about 140 images (Modena cathedral, Italy). The effectiveness of the filtering procedure was verified using some internal quality indicators, external checks (ground truth data) and qualitative visual analyses
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