11,905 research outputs found
Boosted Random ferns for object detection
© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this paper we introduce the Boosted Random Ferns (BRFs) to rapidly build discriminative classifiers for learning and detecting object categories. At the core of our approach we use standard random ferns, but we introduce four main innovations that let us bring ferns from an instance to a category level, and still retain efficiency. First, we define binary features on the histogram of oriented gradients-domain (as opposed to intensity-), allowing for a better representation of intra-class variability. Second, both the positions where ferns are evaluated within the sliding window, and the location of the binary features for each fern are not chosen completely at random, but instead we use a boosting strategy to pick the most discriminative combination of them. This is further enhanced by our third contribution, that is to adapt the boosting strategy to enable sharing of binary features among different ferns, yielding high recognition rates at a low computational cost. And finally, we show that training can be performed online, for sequentially arriving images. Overall, the resulting classifier can be very efficiently trained, densely evaluated for all image locations in about 0.1 seconds, and provides detection rates similar to competing approaches that require expensive and significantly slower processing times. We demonstrate the effectiveness of our approach by thorough experimentation in publicly available datasets in which we compare against state-of-the-art, and for tasks of both 2D detection and 3D multi-view estimation.Peer ReviewedPostprint (author's final draft
Cascaded High Dimensional Histograms: A Generative Approach to Density Estimation
We present tree- and list- structured density estimation methods for high
dimensional binary/categorical data. Our density estimation models are high
dimensional analogies to variable bin width histograms. In each leaf of the
tree (or list), the density is constant, similar to the flat density within the
bin of a histogram. Histograms, however, cannot easily be visualized in higher
dimensions, whereas our models can. The accuracy of histograms fades as
dimensions increase, whereas our models have priors that help with
generalization. Our models are sparse, unlike high-dimensional histograms. We
present three generative models, where the first one allows the user to specify
the number of desired leaves in the tree within a Bayesian prior. The second
model allows the user to specify the desired number of branches within the
prior. The third model returns lists (rather than trees) and allows the user to
specify the desired number of rules and the length of rules within the prior.
Our results indicate that the new approaches yield a better balance between
sparsity and accuracy of density estimates than other methods for this task.Comment: 27 pages, 13 figure
Boosting the Accuracy of Differentially-Private Histograms Through Consistency
We show that it is possible to significantly improve the accuracy of a
general class of histogram queries while satisfying differential privacy. Our
approach carefully chooses a set of queries to evaluate, and then exploits
consistency constraints that should hold over the noisy output. In a
post-processing phase, we compute the consistent input most likely to have
produced the noisy output. The final output is differentially-private and
consistent, but in addition, it is often much more accurate. We show, both
theoretically and experimentally, that these techniques can be used for
estimating the degree sequence of a graph very precisely, and for computing a
histogram that can support arbitrary range queries accurately.Comment: 15 pages, 7 figures, minor revisions to previous versio
Identification of galaxy cluster substructures with the Caustic method
We investigate the power of the caustic technique for identifying
substructures of galaxy clusters from optical redshift data alone. The caustic
technique is designed to estimate the mass profile of galaxy clusters to radii
well beyond the virial radius, where dynamical equilibrium does not hold. Two
by-products of this technique are the identification of the cluster members and
the identification of the cluster substructures. We test the caustic technique
as a substructure detector on two samples of 150 mock redshift surveys of
clusters; the clusters are extracted from a large cosmological -body
simulation of a CDM model and have masses of and in the two
samples. We limit our analysis to substructures identified in the simulation
with masses larger than . With mock redshift surveys
with 200 galaxies within , (1) the caustic technique recovers \% of the real substructures, and (2) \% of the substructures
identified by the caustic technique correspond to real substructures of the
central cluster, the remaining fraction being low-mass substructures, groups or
substructures of clusters in the surrounding region, or chance alignments of
unrelated galaxies. These encouraging results show that the caustic technique
is a promising approach for investigating the complex dynamics of galaxy
clusters.Comment: 13 pages, 15 figures. Accepted for publication in Ap
HBST: A Hamming Distance embedding Binary Search Tree for Visual Place Recognition
Reliable and efficient Visual Place Recognition is a major building block of
modern SLAM systems. Leveraging on our prior work, in this paper we present a
Hamming Distance embedding Binary Search Tree (HBST) approach for binary
Descriptor Matching and Image Retrieval. HBST allows for descriptor Search and
Insertion in logarithmic time by exploiting particular properties of binary
Feature descriptors. We support the idea behind our search structure with a
thorough analysis on the exploited descriptor properties and their effects on
completeness and complexity of search and insertion. To validate our claims we
conducted comparative experiments for HBST and several state-of-the-art methods
on a broad range of publicly available datasets. HBST is available as a compact
open-source C++ header-only library.Comment: Submitted to IEEE Robotics and Automation Letters (RA-L) 2018 with
International Conference on Intelligent Robots and Systems (IROS) 2018
option, 8 pages, 10 figure
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