27,887 research outputs found
A Novel Method for the Absolute Pose Problem with Pairwise Constraints
Absolute pose estimation is a fundamental problem in computer vision, and it
is a typical parameter estimation problem, meaning that efforts to solve it
will always suffer from outlier-contaminated data. Conventionally, for a fixed
dimensionality d and the number of measurements N, a robust estimation problem
cannot be solved faster than O(N^d). Furthermore, it is almost impossible to
remove d from the exponent of the runtime of a globally optimal algorithm.
However, absolute pose estimation is a geometric parameter estimation problem,
and thus has special constraints. In this paper, we consider pairwise
constraints and propose a globally optimal algorithm for solving the absolute
pose estimation problem. The proposed algorithm has a linear complexity in the
number of correspondences at a given outlier ratio. Concretely, we first
decouple the rotation and the translation subproblems by utilizing the pairwise
constraints, and then we solve the rotation subproblem using the
branch-and-bound algorithm. Lastly, we estimate the translation based on the
known rotation by using another branch-and-bound algorithm. The advantages of
our method are demonstrated via thorough testing on both synthetic and
real-world dataComment: 10 pages, 7figure
The removal of shear-ellipticity correlations from the cosmic shear signal: Influence of photometric redshift errors on the nulling technique
Cosmic shear is regarded one of the most powerful probes to reveal the
properties of dark matter and dark energy. To fully utilize its potential, one
has to be able to control systematic effects down to below the level of the
statistical parameter errors. Particularly worrisome in this respect is
intrinsic alignment, causing considerable parameter biases via correlations
between the intrinsic ellipticities of galaxies and the gravitational shear,
which mimic lensing. In an earlier work we have proposed a nulling technique
that downweights this systematic, only making use of its well-known redshift
dependence. We assess the practicability of nulling, given realistic conditions
on photometric redshift information. For several simplified intrinsic alignment
models and a wide range of photometric redshift characteristics we calculate an
average bias before and after nulling. Modifications of the technique are
introduced to optimize the bias removal and minimize the information loss by
nulling. We demonstrate that one of the presented versions is close to optimal
in terms of bias removal, given high quality of photometric redshifts. For
excellent photometric redshift information, i.e. at least 10 bins with a small
dispersion, a negligible fraction of catastrophic outliers, and precise
knowledge about the redshift distributions, one version of nulling is capable
of reducing the shear-intrinsic ellipticity contamination by at least a factor
of 100. Alternatively, we describe a robust nulling variant which suppresses
the systematic signal by about 10 for a very broad range of photometric
redshift configurations. Irrespective of the photometric redshift quality, a
loss of statistical power is inherent to nulling, which amounts to a decrease
of the order 50% in terms of our figure of merit.Comment: 26 pages, including 16 figures; minor changes to match accepted
version; published in Astronomy and Astrophysic
Extrinsic Parameter Calibration for Line Scanning Cameras on Ground Vehicles with Navigation Systems Using a Calibration Pattern
Line scanning cameras, which capture only a single line of pixels, have been
increasingly used in ground based mobile or robotic platforms. In applications
where it is advantageous to directly georeference the camera data to world
coordinates, an accurate estimate of the camera's 6D pose is required. This
paper focuses on the common case where a mobile platform is equipped with a
rigidly mounted line scanning camera, whose pose is unknown, and a navigation
system providing vehicle body pose estimates. We propose a novel method that
estimates the camera's pose relative to the navigation system. The approach
involves imaging and manually labelling a calibration pattern with distinctly
identifiable points, triangulating these points from camera and navigation
system data and reprojecting them in order to compute a likelihood, which is
maximised to estimate the 6D camera pose. Additionally, a Markov Chain Monte
Carlo (MCMC) algorithm is used to estimate the uncertainty of the offset.
Tested on two different platforms, the method was able to estimate the pose to
within 0.06 m / 1.05 and 0.18 m / 2.39. We also propose
several approaches to displaying and interpreting the 6D results in a human
readable way.Comment: Published in MDPI Sensors, 30 October 201
Ground Profile Recovery from Aerial 3D LiDAR-based Maps
The paper presents the study and implementation of the ground detection
methodology with filtration and removal of forest points from LiDAR-based 3D
point cloud using the Cloth Simulation Filtering (CSF) algorithm. The
methodology allows to recover a terrestrial relief and create a landscape map
of a forestry region. As the proof-of-concept, we provided the outdoor flight
experiment, launching a hexacopter under a mixed forestry region with sharp
ground changes nearby Innopolis city (Russia), which demonstrated the
encouraging results for both ground detection and methodology robustness.Comment: 8 pages, FRUCT-2019 conferenc
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