Special Functions and Their Applications. By N. N. Lebedev, translated by R. A. Silverman. Pp. xii, 308. 96s. 1965. (Prentice-Hall)

Compared to diverse feature detectors and descriptors used for visual scenes, describing a place using structural information is relatively less reported. Recent advances in simultaneous localization and mapping (SLAM) provides dense 3D maps of the environment and the localization is proposed by diverse sensors. Toward the global localization based on the structural information, we propose Scan Context, a non-histogram-based global descriptor from 3D Light Detection and Ranging (LiDAR) scans. Unlike previously reported methods, the proposed approach directly records a 3D structure of a visible space from a sensor and does not rely on a histogram or on prior training. In addition, this approach proposes the use of a similarity score to calculate the distance between two scan contexts and also a two-phase search algorithm to efficiently detect a loop. Scan context and its search algorithm make loop-detection invariant to LiDAR viewpoint changes so that loops can be detected in places such as reverse revisit and corner. Scan context performance has been evaluated via various benchmark datasets of 3D LiDAR scans, and the proposed method shows a sufficiently improved performance.

Scan Context: Egocentric Spatial Descriptor for Place Recognition Within 3D Point Cloud Map

This paper introduces a multimodal range dataset namely for radio detection and ranging (radar) and light detection and ranging (LiDAR) specifically targeting the urban environment. By extending our workshop paper [1] to a larger scale, this dataset focuses on the range sensor-based place recognition and provides 6D baseline trajectories of a vehicle for place recognition ground truth. Provided radar data support both raw-level and image-format data, including a set of time-stamped 1D intensity arrays and 360◦ polar images, respectively. In doing so, we provide flexibility between raw data and image data depending on the purpose of the research. Unlike existing datasets, our focus is at capturing both temporal and structural diversities for range-based place recognition research. For evaluation, we applied and validated that our previous location descriptor and its search algorithm [2] are highly effective for radar place recognition method. Furthermore, the result shows that radar-based place recognition outperforms LiDAR-based one exploiting its longer-range measurements. The dataset is available from https://sites.google.com/view/mulran-pr

MulRan: Multimodal Range Dataset for Urban Place Recognition

Underwater manipulators: a review

The powerful representation capacity of deep learning has made it inevitable for the underwater image enhancement community to employ its potential. The exploration of deep underwater image enhancement networks is increasing over time; hence, a comprehensive survey is the need of the hour. In this paper, our main aim is two-fold, (1): to provide a comprehensive and in-depth survey of the deep learning-based underwater image enhancement, which covers various perspectives ranging from algorithms to open issues, and (2): to conduct a qualitative and quantitative comparison of the deep algorithms on diverse datasets to serve as a benchmark, which has been barely explored before. We first introduce the underwater image formation models, which are the base of training data synthesis and design of deep networks, and also helpful for understanding the process of underwater image degradation. Then, we review deep underwater image enhancement algorithms, and a glimpse of some of the aspects of the current networks is presented, including architecture, parameters, training data, loss function, and training configurations. We also summarize the evaluation metrics and underwater image datasets. Following that, a systematically experimental comparison is carried out to analyze the robustness and effectiveness of deep algorithms. Meanwhile, we point out the shortcomings of current benchmark datasets and evaluation metrics. Finally, we discuss several unsolved open issues and suggest possible research directions. We hope that all efforts done in this paper might serve as a comprehensive reference for future research and call for the development of deep learning-based underwater image enhancement.

Diving deeper into underwater image enhancement: A survey

In this paper, we investigate the potential of vision-based object detection algorithms in underwater environments using several datasets to highlight the issues arising in different scenarios. Und...

https://journals.sagepub.com/doi/pdf/10.5772/60526

Investigation of Vision-Based Underwater Object Detection with Multiple Datasets

Detecting features in sensor measurements and distinguishing among them is an important capability for robot localization and navigation. Despite the wide diffusion of range finders, there are few works on keypoint features for 2-D LIDAR and there is potential for improvement over the existing methods. This letter proposes two novel keypoint detectors for the stable detection of interest points in laser measurements and two descriptors for robust associations. The features defined by combining keypoints and descriptors allow stable and efficient place recognition. Experiments with standard benchmark datasets assess the performance of the detectors and descriptors investigated. One of the proposed features, termed FALKO-BSC, achieves higher repeatability score and similar descriptor performance compared with the FLIRT state-of-the-art feature. FALKO-BSC is also shown to enable effective localization.

Fast Keypoint Features From Laser Scanner for Robot Localization and Mapping

Autonomous underwater vehicles are frequently used for survey missions and monitoring tasks, however, manipulation and intervention tasks are still largely performed with a human in the loop. Employing autonomous vehicles for these tasks has received a growing interest in the last ten years, and few pioneering projects have been funded on this topic. Among these projects, the Italian MARIS project had the goal of developing technologies and methodologies for the use of autonomous underwater vehicle manipulator systems in underwater manipulation and transportation tasks. This work presents the developed control framework, the mechatronic integration, and the project's final experimental results on floating underwater intervention.

/pdf/autonomous-underwater-intervention-experimental-results-of-2bbdgn7p9q.pdf

Autonomous Underwater Intervention: Experimental Results of the MARIS Project

Integration of a stereo vision system into an autonomous underwater vehicle for pipe manipulation tasks

Keypoint features detection from measurements enables efficient localization and map estimation through the compact representation and recognition of locations. The keypoint detector FALKO has been proposed to detect stable points in laser scans for localization and mapping tasks. In this paper, we present novel loop closure methods based on FALKO keypoints and compare their performance in online localization and mapping problems. The pose graph formulation is adopted, where each pose is associated to a local map of keypoints extracted from the corresponding laser scan. Loops in the graph are detected by matching local maps in two steps. First, the candidate matching scans are selected by comparing the scan signatures obtained from the keypoints of each scan. Second, the transformation between two scans is obtained by pairing and aligning the respective keypoint sets. Experiments with standard benchmark datasets assess the performance of FALKO and of the proposed loop closure algorithms in both offline and online localization and map estimation.

Dario Lodi Rizzini

Papers

Investigation of Vision-Based Underwater Object Detection with Multiple Datasets

Fast Keypoint Features From Laser Scanner for Robot Localization and Mapping

Autonomous Underwater Intervention: Experimental Results of the MARIS Project

Integration of a stereo vision system into an autonomous underwater vehicle for pipe manipulation tasks

Efficient loop closure based on FALKO lidar features for online robot localization and mapping