19,455 research outputs found
VConv-DAE: Deep Volumetric Shape Learning Without Object Labels
With the advent of affordable depth sensors, 3D capture becomes more and more
ubiquitous and already has made its way into commercial products. Yet,
capturing the geometry or complete shapes of everyday objects using scanning
devices (e.g. Kinect) still comes with several challenges that result in noise
or even incomplete shapes. Recent success in deep learning has shown how to
learn complex shape distributions in a data-driven way from large scale 3D CAD
Model collections and to utilize them for 3D processing on volumetric
representations and thereby circumventing problems of topology and
tessellation. Prior work has shown encouraging results on problems ranging from
shape completion to recognition. We provide an analysis of such approaches and
discover that training as well as the resulting representation are strongly and
unnecessarily tied to the notion of object labels. Thus, we propose a full
convolutional volumetric auto encoder that learns volumetric representation
from noisy data by estimating the voxel occupancy grids. The proposed method
outperforms prior work on challenging tasks like denoising and shape
completion. We also show that the obtained deep embedding gives competitive
performance when used for classification and promising results for shape
interpolation
Colour-colour diagrams and extragalactic globular cluster ages. Systematic uncertainties using the (V-K)-(V-I) diagram
(abridged) We investigate biases in cluster ages and [Fe/H] estimated from
the (V-K)-(V-I) diagram, arising from inconsistent Horizontal Branch
morphology, metal mixture, treatment of core convection between observed
clusters and the theoretical colour grid employed for age and metallicity
determinations. We also study the role played by statistical fluctuations of
the observed colours, caused by the low total mass of typical globulars.
Horizontal Branch morphology is potentially the largest source of uncertainty.
A single-age system harbouring a large fraction of clusters with an HB
morphology systematically bluer than the one accounted for in the theoretical
colour grid, can simulate a bimodal population with an age difference as large
as 8 Gyr. When only the redder clusters are considered, this uncertainty is
almost negligible, unless there is an extreme mass loss along the Red Giant
Branch phase. The metal mixture affects mainly the redder clusters; the effect
of colour fluctuations becomes negligible for the redder clusters, or when the
integrated Mv is brighter than -8.5 mag. The treatment of core convection is
relevant for ages below ~4 Gyr. The retrieved [Fe/H] distributions are overall
only mildly affected. Colour fluctuations and convective core extension have
the largest effect. When 1sigma photometric errors reach 0.10 mag, all biases
found in our analysis are erased, and bimodal age populations with age
differences of up to ~8 Gyr go undetected. The use of both (U-I)-(V-K) and
(V-I)-(V-K) diagrams may help disclosing the presence of blue HB stars
unaccounted for in the theoretical colour calibration.Comment: 20 pages, including 26 figures. A&A in pres
Unsupervised Monocular Depth Estimation with Left-Right Consistency
Learning based methods have shown very promising results for the task of
depth estimation in single images. However, most existing approaches treat
depth prediction as a supervised regression problem and as a result, require
vast quantities of corresponding ground truth depth data for training. Just
recording quality depth data in a range of environments is a challenging
problem. In this paper, we innovate beyond existing approaches, replacing the
use of explicit depth data during training with easier-to-obtain binocular
stereo footage.
We propose a novel training objective that enables our convolutional neural
network to learn to perform single image depth estimation, despite the absence
of ground truth depth data. Exploiting epipolar geometry constraints, we
generate disparity images by training our network with an image reconstruction
loss. We show that solving for image reconstruction alone results in poor
quality depth images. To overcome this problem, we propose a novel training
loss that enforces consistency between the disparities produced relative to
both the left and right images, leading to improved performance and robustness
compared to existing approaches. Our method produces state of the art results
for monocular depth estimation on the KITTI driving dataset, even outperforming
supervised methods that have been trained with ground truth depth.Comment: CVPR 2017 ora
Strongly lensed SNe Ia in the era of LSST: observing cadence for lens discoveries and time-delay measurements
The upcoming Large Synoptic Survey Telescope (LSST) will detect many strongly
lensed Type Ia supernovae (LSNe Ia) for time-delay cosmography. This will
provide an independent and direct way for measuring the Hubble constant ,
which is necessary to address the current tension in between
the local distance ladder and the early Universe measurements. We present a
detailed analysis of different observing strategies for the LSST, and quantify
their impact on time-delay measurement between multiple images of LSNe Ia. For
this, we produced microlensed mock-LSST light curves for which we estimated the
time delay between different images. We find that using only LSST data for
time-delay cosmography is not ideal. Instead, we advocate using LSST as a
discovery machine for LSNe Ia, enabling time delay measurements from follow-up
observations from other instruments in order to increase the number of systems
by a factor of 2 to 16 depending on the observing strategy. Furthermore, we
find that LSST observing strategies, which provide a good sampling frequency
(the mean inter-night gap is around two days) and high cumulative season length
(ten seasons with a season length of around 170 days per season), are favored.
Rolling cadences subdivide the survey and focus on different parts in different
years; these observing strategies trade the number of seasons for better
sampling frequency. In our investigation, this leads to half the number of
systems in comparison to the best observing strategy. Therefore rolling
cadences are disfavored because the gain from the increased sampling frequency
cannot compensate for the shortened cumulative season length. We anticipate
that the sample of lensed SNe Ia from our preferred LSST cadence strategies
with rapid follow-up observations would yield an independent percent-level
constraint on .Comment: 25 pages, 22 figures; accepted for publication in A&
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