Visual–inertial odometry (VIO) is widely studied and used in autonomous robots. This article proposes a novel tightly coupled monocular VIO system based on point-line constraints (PLC-VIO). In the front end, PLC-VIO presents a line segment extraction and merging algorithm based on the EDLines method and achieves real-time feature tracking based on the geometric constraints between feature points and lines. In the back end, PLC-VIO reconstructs new 3-D landmarks of feature lines through points on the line and optimizes the states by minimizing a cost function that combines the preintegrated inertial measurement unit (IMU) error term together with the point and line reprojection error terms in a sliding window optimization framework. A loop closure module is also integrated, which enables relocalization and drift elimination. The corresponding experimental evaluations are conducted using public datasets to validate the effectiveness and robustness of the proposed system, and the results show that PLC-VIO can achieve good performance when compared with other state-of-the-art systems and, at the same time, with no compromise to real-time performance. Note to Practitioners —Visual–inertial odometry (VIO) can estimate the states of the rigid body (including position, attitude, and velocity) that is widely used in robotic navigation, autonomous driving, virtual reality (VR), and augmented reality (AR). Aiming at the problem of estimating the states of autonomous robots in the GPS-denied environment, this article proposes a novel VIO system based on the point-line constraints (PLC-VIO). PLC-VIO can not only achieve accurate pose estimation for robots due to the introduction of the line features but also make no concession to real-time performance. Furthermore, PLC-VIO can also enrich the texture features of the environment during the 3-D mapping construction. The corresponding experiments are implemented in public datasets to evaluate the effectiveness, efficiency, and robustness of the proposed system. We believe that PLC-VIO can be widely used in robotic navigation and AR/VR fields to provide accurate position and environment information in real time.

To solve the problem of inaccurate orientation estimation after long-term operations of the Inertial Measurement Unit (IMU), we present a learning-based method (called Gyro-Net) to estimate and compensate for IMU gyroscope random errors. We firstly introduce a semi-dense network structure, which extracts different scale features by IFES Block (IMU Feature Extraction & Selection Block), and adopts skip-connections and transition layers to adjust the feature pipeline. In this way, we can reuse features between different blocks before and after feature extraction, selection and compression. Driven by a proposed absolute and relative loss, the network can be trained and achieve the reduction of cumulative estimated orientation errors. The experimental results in public datasets show that our method can effectively and accurately estimate the orientation from raw IMU data. Moreover, we apply the network output directly to Open-VINS, and the results show that Gyro-Net can improve the accuracy of pose estimation for Open-VINS, especially in scenarios where camera-based estimation often struggles (e.g., fast motion, drastic lighting, viewpoint changes and motion blur).

The emerging event cameras are bio-inspired sensors that can output pixel-level brightness changes at extremely high rates, and event-based visual-inertial odometry (VIO) is widely studied and used in autonomous robots. In this paper, we propose an event-based stereo VIO system, namely ESVIO. Firstly, we present a novel direct event-based VIO method, which fuses events’ depth, Time-Surface images, and pre-integrated inertial measurement to estimate the camera motion and inertial measurement unit (IMU) biases in a sliding window non-linear optimization framework, effectively improving the state estimation accuracy and robustness. Secondly, we design an event-inertia semi-joint initialization method, through two steps of event-only initialization and event-inertia initial optimization, to rapidly and accurately solve the initialization parameters of the VIO system, thereby further improving the state estimation accuracy. Based on these two methods, we implement the ESVIO system and evaluate the effectiveness and robustness of ESVIO on various public datasets. The experimental results show that ESVIO achieves good performance in both accuracy and robustness when compared with other state-of-the-art event-based VIO and stereo visual odometry (VO) systems, and, at the same time, with no compromise to real-time performance.

UAV-to-satellite geolocalization offers accurate drift-free navigation in the absence of external positioning signals. Increased deep-learning-based approaches have demonstrated their potential for high accuracy by framing the problem as a one-to-all retrieval task. However, in real-world scenario, the problem is not just a one-to-all retrieval task, which leads to a gap between research and applications. Based on this observation, We attempt to look closer to the problem instead of designing sophisticated network architectures or objective functions. In this study, we proposed a flexible and simple coarse-to-fine sequence-matching solution with targeted joint use of deep learning and classical machine learning approaches. Our goal is to improve geolocalization accuracy by matching UAV images with a few relevant reference image patches instead of all images. To this end, we first coarsely constructed a sequence of reference satellite image patches corresponding to the UAV trajectory, for which we proposed a deep feature- and manifold learning-based image-sorting method. Once the reference satellite patches are sorted and aligned with the UAV trajectory, the reference sequence is determined. Given a query UAV frame, the search area can be decreased from two to one dimensions. In particular, both deep-learning-based and classical image-matching algorithms can provide competitive accuracy when integrating sequence constraints. We demonstrate that classical manifold learning-based and image matching methods perform exceptionally well for UAV-to-satellite geolocalization when utilized jointly with suitable deep learning techniques. We validated the approach’s unique outperformance on two challenging and realistic UAV-to-satellite geolocalization datasets. Dataset, code and models are available for research purposes at https://seqmatch.geovisuallocalization.com/.

In recent years, self-supervised paradigms for depth estimation have drawn lots of attention from the community. Promising as they are, in order to achieve wider application and better performance, reasoning about the uncertainty of the estimated depth maps is in great demand. In this paper, we propose a novel uncertainty-aware self-improving framework for self-supervised depth estimation, which could model and exploit uncertainty to boost depth accuracy without any external supervision. In detail, our framework includes two DepthNets–a teacher network and a student network. The teacher network is pre-trained in a self-supervised manner and the predicted depth is leveraged as pseudo-ground-truth to supervise the learning of the student network, leading to better estimation accuracy and the ability of modeling depth uncertainty. Afterward, the estimated uncertainty would be introduced back into the teacher network as the mask, preventing erroneous regions from contributing to network training and depth estimation. In this way, a better pseudo-ground-truth from the teacher network will be used for the next iteration of the student network training. We evaluate our proposed framework on the widely used KITTI dataset and TUM RGB-D dataset with both quantitative and qualitative experiments. The experimental results show that our framework achieves quite satisfactory performance among the self-supervised depth estimation methods. Extensive experiments which combine the student network and feature-based monocular SLAM system (i.e ORB-SLAM3) further demonstrate the benefits of the introduced depth uncertainty.

The emerging event cameras have the potential to be an excellent complement for standard cameras within various visual tasks, especially in illumination‐changing environments or situations requiring high‐temporal resolution. Herein, an event‐based stereo visual odometry (VO) system via adaptive time‐surface (TS) and truncated signed distance function (TSDF), namely, T‐ESVO, is proposed . The system consists of three carefully designed components, including the event processing unit, the mapping unit, and the tracking unit. Specifically, the event processing unit adopts a novel spatial–temporal adaptive TS that can deal with different camera motions in various environments. The mapping unit introduces the TSDF to describe the 3D representation of environments and achieves depth estimation based on the global historical depth information contained in the environmental TSDF description. The tracking unit achieves the 6‐DoF pose estimation through an 3D–2D registration method based on the left/right TS selection mechanism and the depth point selection mechanism. The effectiveness and robustness of the proposed system are evaluated on various datasets, and the experimental results show that T‐ESVO achieves good performance in both accuracy and robustness when compared with other state‐of‐the‐art event‐based stereo VO systems.