5 research outputs found
OSPC: Online Sequential Photometric Calibration
Photometric calibration is essential to many computer vision applications.
One of its key benefits is enhancing the performance of Visual SLAM, especially
when it depends on a direct method for tracking, such as the standard KLT
algorithm. Another advantage could be in retrieving the sensor irradiance
values from measured intensities, as a pre-processing step for some vision
algorithms, such as shape-from-shading. Current photometric calibration systems
rely on a joint optimization problem and encounter an ambiguity in the
estimates, which can only be resolved using ground truth information. We
propose a novel method that solves for photometric parameters using a
sequential estimation approach. Our proposed method achieves high accuracy in
estimating all parameters; furthermore, the formulations are linear and convex,
which makes the solution fast and suitable for online applications. Experiments
on a Visual Odometry system validate the proposed method and demonstrate its
advantages
H-SLAM: Hybrid Direct-Indirect Visual SLAM
The recent success of hybrid methods in monocular odometry has led to many
attempts to generalize the performance gains to hybrid monocular SLAM. However,
most attempts fall short in several respects, with the most prominent issue
being the need for two different map representations (local and global maps),
with each requiring different, computationally expensive, and often redundant
processes to maintain. Moreover, these maps tend to drift with respect to each
other, resulting in contradicting pose and scene estimates, and leading to
catastrophic failure. In this paper, we propose a novel approach that makes use
of descriptor sharing to generate a single inverse depth scene representation.
This representation can be used locally, queried globally to perform loop
closure, and has the ability to re-activate previously observed map points
after redundant points are marginalized from the local map, eliminating the
need for separate and redundant map maintenance processes. The maps generated
by our method exhibit no drift between each other, and can be computed at a
fraction of the computational cost and memory footprint required by other
monocular SLAM systems. Despite the reduced resource requirements, the proposed
approach maintains its robustness and accuracy, delivering performance
comparable to state-of-the-art SLAM methods (e.g., LDSO, ORB-SLAM3) on the
majority of sequences from well-known datasets like EuRoC, KITTI, and TUM VI.
The source code is available at: https://github.com/AUBVRL/fslam_ros_docker
SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study
Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling.
Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty.
Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year.
Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population