28,584 research outputs found
Find your Way by Observing the Sun and Other Semantic Cues
In this paper we present a robust, efficient and affordable approach to
self-localization which does not require neither GPS nor knowledge about the
appearance of the world. Towards this goal, we utilize freely available
cartographic maps and derive a probabilistic model that exploits semantic cues
in the form of sun direction, presence of an intersection, road type, speed
limit as well as the ego-car trajectory in order to produce very reliable
localization results. Our experimental evaluation shows that our approach can
localize much faster (in terms of driving time) with less computation and more
robustly than competing approaches, which ignore semantic information
Localization of short duration gravitational-wave transients with the early advanced LIGO and Virgo detectors
The Laser Interferometer Gravitational wave Observatory (LIGO) and Virgo,
advanced ground-based gravitational-wave detectors, will begin collecting
science data in 2015. With first detections expected to follow, it is important
to quantify how well generic gravitational-wave transients can be localized on
the sky. This is crucial for correctly identifying electromagnetic counterparts
as well as understanding gravitational-wave physics and source populations. We
present a study of sky localization capabilities for two search and parameter
estimation algorithms: \emph{coherent WaveBurst}, a constrained likelihood
algorithm operating in close to real-time, and \emph{LALInferenceBurst}, a
Markov chain Monte Carlo parameter estimation algorithm developed to recover
generic transient signals with latency of a few hours. Furthermore, we focus on
the first few years of the advanced detector era, when we expect to only have
two (2015) and later three (2016) operational detectors, all below design
sensitivity. These detector configurations can produce significantly different
sky localizations, which we quantify in detail. We observe a clear improvement
in localization of the average detected signal when progressing from
two-detector to three-detector networks, as expected. Although localization
depends on the waveform morphology, approximately 50% of detected signals would
be imaged after observing 100-200 deg in 2015 and 60-110 deg in 2016,
although knowledge of the waveform can reduce this to as little as 22 deg.
This is the first comprehensive study on sky localization capabilities for
generic transients of the early network of advanced LIGO and Virgo detectors,
including the early LIGO-only two-detector configuration.Comment: 18 pages, 8 figure
Cross-View Image Matching for Geo-localization in Urban Environments
In this paper, we address the problem of cross-view image geo-localization.
Specifically, we aim to estimate the GPS location of a query street view image
by finding the matching images in a reference database of geo-tagged bird's eye
view images, or vice versa. To this end, we present a new framework for
cross-view image geo-localization by taking advantage of the tremendous success
of deep convolutional neural networks (CNNs) in image classification and object
detection. First, we employ the Faster R-CNN to detect buildings in the query
and reference images. Next, for each building in the query image, we retrieve
the nearest neighbors from the reference buildings using a Siamese network
trained on both positive matching image pairs and negative pairs. To find the
correct NN for each query building, we develop an efficient multiple nearest
neighbors matching method based on dominant sets. We evaluate the proposed
framework on a new dataset that consists of pairs of street view and bird's eye
view images. Experimental results show that the proposed method achieves better
geo-localization accuracy than other approaches and is able to generalize to
images at unseen locations
TDoA-based outdoor positioning in a public LoRa network
The performance of LoRa Geo-location for outdoor tracking purposes has been evaluated on a public LoRaWAN network. Time Difference of Arrival (TDOA) localization accuracy, probability and update frequency were evaluated for different trajectories (walking, cycling, driving) and LoRa spreading factors. A median accuracy of 200m was obtained and in 90% of the cases the error was less then 480m
Cluster-Wise Ratio Tests for Fast Camera Localization
Feature point matching for camera localization suffers from scalability
problems. Even when feature descriptors associated with 3D scene points are
locally unique, as coverage grows, similar or repeated features become
increasingly common. As a result, the standard distance ratio-test used to
identify reliable image feature points is overly restrictive and rejects many
good candidate matches. We propose a simple coarse-to-fine strategy that uses
conservative approximations to robust local ratio-tests that can be computed
efficiently using global approximate k-nearest neighbor search. We treat these
forward matches as votes in camera pose space and use them to prioritize
back-matching within candidate camera pose clusters, exploiting feature
co-visibility captured by clustering the 3D model camera pose graph. This
approach achieves state-of-the-art camera localization results on a variety of
popular benchmarks, outperforming several methods that use more complicated
data structures and that make more restrictive assumptions on camera pose. We
also carry out diagnostic analyses on a difficult test dataset containing
globally repetitive structure that suggest our approach successfully adapts to
the challenges of large-scale image localization
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