Hasil untuk "Canals and inland navigation. Waterways"

Zedong Chu, Shichao Xie, Xiaolong Wu et al.

Embodied navigation has long been fragmented by task-specific architectures. We introduce ABot-N0, a unified Vision-Language-Action (VLA) foundation model that achieves a ``Grand Unification'' across 5 core tasks: Point-Goal, Object-Goal, Instruction-Following, POI-Goal, and Person-Following. ABot-N0 utilizes a hierarchical ``Brain-Action'' architecture, pairing an LLM-based Cognitive Brain for semantic reasoning with a Flow Matching-based Action Expert for precise, continuous trajectory generation. To support large-scale learning, we developed the ABot-N0 Data Engine, curating 16.9M expert trajectories and 5.0M reasoning samples across 7,802 high-fidelity 3D scenes (10.7 $\text{km}^2$). ABot-N0 achieves new SOTA performance across 7 benchmarks, significantly outperforming specialized models. Furthermore, our Agentic Navigation System integrates a planner with hierarchical topological memory, enabling robust, long-horizon missions in dynamic real-world environments.

Neeti Sonth, Jade Morton, Logan Scott

This paper provides a theoretical examination of tropospheric effects on signals at the L, S, C, X, and Ku bands across four distinct regions characterized by diverse climates. Specifically, we investigate Indonesia, situated near the equator and renowned for its exceptionally high rainfall; Norway, a polar region with markedly dry conditions; Boulder, Colorado, a mid-latitude area with a relatively arid climate; and Maui, Hawaii, a low-latitude locale known for its relatively wet climate. This paper summarizes an analysis of total delay and attenuation. The analysis includes (1) the variation in total delay with elevation angle, (2) effects of attenuation stemming from atmospheric phenomena such as rain, clouds, and gases, and (3) amplitude fading due to scintillation. The modeling shows that the effects increase with increasing frequency and decreasing elevation angle. Further, the assessment suggests that gaseous attenuation can be ignored for our frequencies of interest but that the other tropospheric effects must be accounted for.

Richard B. Langley

Welcome to the Summer 2025 issue of NAVIGATION. As geopolitical events continue to be front and center these days, almost half of the articles in this issue deal with aspects of GNSS integrity. We also have an article on the development and maintenance of the World Geodetic System 1984 – the terrestrial reference frame used by GPS – and its alignment to the International Terrestrial Reference Frame. And we have another article on the use of low Earth orbiting satellites for positioning and navigation. And, as always, a great deal more.

Ali Hassani, Mathieu Joerger

This paper describes the design, analysis, and experimental evaluation of a spherical grid-based localization algorithm that leverages quantization theory to bound navigation uncertainty. This algorithm integrates data from light detection and ranging (lidar) and inertial measuring units in an iterative extended Kalman filter to estimate the position and orientation of a moving vehicle. An analytical bound is derived from the vehicle’s state estimation error, which accounts for both random measurement noise and the loss of localization information caused by gridding. The performance of the proposed approach is analyzed and compared with that of a brute-force spherical grid-based method and a landmark-based method in an indoor environment, whereas an outdoor experiment verifies the practicality of the method in a realistic driving scenario.

Nacer Naciri, Yoaz Bar-Sever, Willy Bertiger et al.

In the current global navigation satellite system (GNSS) context, with several constellations offering high accuracy services (HAS), we have evaluated a potential HAS for GPS based on JPL’s Global Differential GPS (GDGPS) system. This HAS also provides corrections for Galileo and GLONASS. In this paper, we specifically consider the scenario in which satellite corrections are delivered to users through the internet, similar to one style of access used for Galileo HAS. The GDGPS-based HAS described herein consists primarily of high-quality satellite orbit and clock corrections and currently excludes code and phase biases. Corrections are provided in two parallel variations: one stream supporting GPS and Galileo, and the other supporting GPS and GLONASS. Each variation is provided in two redundant instances for robustness, giving a total of four streams. Our results, including PPP solutions based on these products, attest to the quality of the corrections. PPP results show good performance, comparable to solutions generated based on real-time CNES products and better than solutions generated based on internet-based Galileo HAS products. For example, based on processing over 2,000 independent three-hour data sets, both the GDGPS-based HAS GPS+GAL streams and the CNES stream achieved post-convergence horizontal rms below 20 cm for 97% of data sets and below 10 cm for 80%. In contrast, only 86% of Galileo HAS-based solutions have post-convergence horizontal rms below 20 cm, and only 47% have rms below 10 cm. Overall, these results suggest a promising method of implementing a GDGPS-based HAS that might augment GPS, Galileo, and GLONASS.

Toru Takahashi, Susumu Saito, Mitsunori Kitamura et al.

The main objective of this study was to evaluate the performance of a dual-frequency multi-constellation (DFMC) satellite-based augmentation system (SBAS) broadcast from the Japanese Quasi-Zenith Satellite System (QZSS) in the Arctic and high-latitude regions. We installed a global navigation satellite system (GNSS) antenna and receiver on the roof of the Kjemibygningen (chemistry building) at the University of Oslo, Norway, on February 24, 2021, and conducted experiments continuously until March 17, 2021. We found that the QZSS-based DFMC SBAS achieved a system availability of 84.68% for localizer performance with vertical guidance when the horizontal and vertical alert limits were set to 40 and 50 m, respectively. This result is below the performance of QZSS-based DFMC SBAS in Japan. However, our analysis shows that adding three or more QZSS reference stations in Europe will enable DFMC SBAS from QZSS to reach 100% availability.

Odile Maliet, Kin Mimouni, Julie Antic et al.

The need for highly reliable positioning in safety-of-life applications has led to the development of global navigation satellite system (GNSS) augmentation systems such as satellite-based augmentation systems and advanced receiver autonomous integrity monitoring. These systems rely on a transfer of integrity from the range to the position domain through concepts such as cumulative distribution function (CDF) overbounding and the more recent two-step overbounding. Here, we propose a new approach, wide-sense CDF overbounding, which offers more flexibility and robustness than existing methods by accommodating biased distributions and relaxing stringent assumptions of symmetry and unimodality while retaining the original simplicity of CDF overbounding. This method combines CDF and paired overbounding, adjusting protection volumes with a formula to compensate for weaker assumptions. We perform numerical analyses using real GNSS data that demonstrate the enhanced flexibility of wide-sense CDF overbounding and show its potential to improve the robustness and performance of GNSS-based safety solutions in various applications.

Sobhan Teymouri, Fatemeh Alizadehziri, Mobina Zibandehpoor et al.

Spatial navigation is a complex cognitive function involving sensory inputs, such as visual, auditory, and proprioceptive information, to understand and move within space. This ability allows humans to create mental maps, navigate through environments, and process directional cues, crucial for exploring new places and finding one's way in unfamiliar surroundings. This study takes an algorithmic approach to extract indices relevant to human spatial navigation using eye movement data. Leveraging electrooculography signals, we analyzed statistical features and applied feature engineering techniques to study eye movements during navigation tasks. The proposed work combines signal processing and machine learning approaches to develop indices for navigation and orientation, spatial anxiety, landmark recognition, path survey, and path route. The analysis yielded five subscore indices with notable accuracy. Among these, the navigation and orientation subscore achieved an R2 score of 0.72, while the landmark recognition subscore attained an R2 score of 0.50. Additionally, statistical features highly correlated with eye movement metrics, including blinks, saccades, and fixations, were identified. The findings of this study can lead to more cognitive assessments and enable early detection of spatial navigation impairments, particularly among individuals at risk of cognitive decline.

Abhishek Dhyani, Amirreza Haqshenas Mojaveri, Chengqian Zhang et al.

This paper introduces AUTOBargeSim, a simulation toolbox for autonomous inland vessel guidance and control system design. AUTOBargeSim is developed using MATLAB and provides an easy-to-use introduction to various aspects of autonomous inland navigation, including mapping, modelling, control design, and collision avoidance, through examples and extensively documented code. Applying modular design principles in the simulator structure allows it to be easily modified according to the user's requirements. Furthermore, a GUI interface facilitates a simple and quick execution. Key performance indices for evaluating the performance of the controller and collision avoidance method in confined space are also provided. The current version of AUTOBargeSim attempts to improve reproducibility in the design and simulation of marine systems while serving as a foundation for simulating and evaluating vessel behaviour considering operational, system, and environmental constraints.

Hoang Anh Tran, Nikolai Lauvås, Tor Arne Johansen et al.

This paper focuses on the problem of collaborative collision avoidance for autonomous inland ships. Two solutions are provided to solve the problem in a distributed manner. We first present a distributed model predictive control (MPC) algorithm that allows ships to directly negotiate their intention to avoid collision in a synchronous communication framework. Moreover, we introduce a new approach to shape the ship's behavior to follow the waterway traffic regulations. The conditional convergence toward a stationary solution of this algorithm is guaranteed by the theory of the Alternating Direction Method of Multipliers (ADMM). To overcome the problem of asynchronous communication between ships, we adopt a new asynchronous nonlinear ADMM and present an asynchronous distributed MPC algorithm based on it. Several simulations and field experiments show that the proposed algorithms can prevent ship collisions even in complex scenarios.

Muhammad Asad Ullah, Vadim Kramar, Hamada Alshaer et al.

Communication, Navigation, and Surveillance (CNS) is the backbone of the Air Traffic Management (ATM) and Unmanned Aircraft System (UAS) Traffic Management (UTM) systems, ensuring safe and efficient operations of modern and future aviation. Traditionally, the CNS is considered three independent systems: communications, navigation, and surveillance. The current CNS system is fragmented, with limited integration across its three domains. Integrated CNS (ICNS) is a contemporary concept implying that those systems are provisioned through the same technology stack. ICNS is envisioned to improve service quality, spectrum efficiency, communication capacity, navigation predictability, and surveillance capabilities. The 5G technology stack offers higher throughput, lower latency, and massive connectivity compared to many existing communication technologies. This paper presents our 5G ICNS vision and network architecture and discusses how 5G technology can support integrated CNS services using terrestrial and non-terrestrial networks. We also discuss key 5G radio access technologies for delivering integrated CNS services at low altitudes for Innovative Air Mobility (IAM) and Advanced Air Mobility (AAM) operations. Finally, we present relevant challenges and potential research directions for further studies.

Zhangyuan Wang, Yunpeng Zhu, Yuqi Yan et al.

This paper presents UnderwaterVLA, a novel framework for autonomous underwater navigation that integrates multimodal foundation models with embodied intelligence systems. Underwater operations remain difficult due to hydrodynamic disturbances, limited communication bandwidth, and degraded sensing in turbid waters. To address these challenges, we introduce three innovations. First, a dual-brain architecture decouples high-level mission reasoning from low-level reactive control, enabling robust operation under communication and computational constraints. Second, we apply Vision-Language-Action(VLA) models to underwater robotics for the first time, incorporating structured chain-of-thought reasoning for interpretable decision-making. Third, a hydrodynamics-informed Model Predictive Control(MPC) scheme compensates for fluid effects in real time without costly task-specific training. Experimental results in field tests show that UnderwaterVLA reduces navigation errors in degraded visual conditions while maintaining higher task completion by 19% to 27% over baseline. By minimizing reliance on underwater-specific training data and improving adaptability across environments, UnderwaterVLA provides a scalable and cost-effective path toward the next generation of intelligent AUVs.

Quanrun Cheng, Junping Chen, Yize Zhang et al.

With advancements in the broadcast ephemeris accuracy of global navigation satellite systems (GNSSs), precise point positioning based on broadcast ephemeris (BE-PPP) is gradually showing promising prospects. However, the periodic updates of GNSS ephemeris result in discontinuities in the satellite orbit and clock offset during handovers. These discontinuities can significantly impact positioning accuracy. In this study, we calculate the combined ephemeris discontinuities, which indicate a linear combination of satellite radial orbit and clock discontinuities. We then compensate for the combined ephemeris discontinuities in the subsequent satellite clocks prior to positioning. For BeiDou Navigation Satellite System 3 (BDS-3) and the Global Positioning System (GPS), the three-dimensional (3D) position accuracy in kinematic mode is improved by 30–50 cm, reaching 33.9 cm. For GPS/Galileo/BDS-3 triple-constellation kinematic solutions, the accuracy reaches 23.2 cm. In static mode, the 3D position accuracy is 14.6 cm for BDS-3-only positioning and 15.1 cm for GPS. For GPS/Galileo/BDS-3 triple-constellation static BE-PPP solutions, the 3D position accuracy improves to 8 cm.

Yu Nakajima, Toru Yamamoto

This paper presents an innovative approach aimed at enhancing satellite position determination accuracy within a geostationary equatorial orbit (GEO) by integrating a regional navigation satellite system (RNSS) with a global navigation satellite system (GNSS). In a GEO, incoming GNSS signals are typically constrained to a specific direction on the other side of the Earth, resulting in a significant dilution of precision (DOP) and, consequently, a significant radial error. By incorporating an RNSS, signals from more diverse directions are available, improving observability and enhancing navigation precision. Taking the quasi-zenith satellite system (QZSS) as a representative RNSS, this paper demonstrates the feasibility of receiving signals from GEO satellites across a substantial range. Link budget analyses were conducted using the precise side-lobe patterns of the QZSS, revealing that QZSS signals can be consistently observed across most arcs in a GEO. Two comprehensive simulations were conducted: a point solution and an extended Kalman filter-based orbit determination. The results affirm the anticipated improvement in navigation precision indicated by the DOP analysis. It is essential to note that whereas RNSS signals can be received from any longitude in a GEO, enhanced navigation precision relies on the distance from the satellite to the RNSS. Considering the availability of multiple RNSS options, the concept presented in this research can be adapted to any longitude within a GEO, thereby promoting stable, high-precision navigation.

Xin Zhang, Xingqun Zhan, Jihong Huang et al.

Tightness remains the primary goal in all modern estimation bounds. For very weak signals, tightness is enabled by appropriately selecting the prior probability distribution and bound family. While current bounds in global navigation satellite systems (GNSSs) assess the performance of carrier frequency estimators under Gaussian or uniform assumptions, the circular nature of frequency is overlooked. Of all bounds in the Bayesian framework, the Weiss–Weinstein bound (WWB) stands out because it is free from regularity conditions or restrictions on the prior distribution. Therefore, the WWB is extended for the current frequency estimation problem. A divide-and-conquer type of hyperparameter tuning method is developed to mitigate issues of computational complexity for the WWB family while enhancing tightness. Synthetic results show that for a von Mises prior probability distribution, the WWB provides a bound up to 22.5% tighter than the Ziv–Zakaï bound when the signal-to-noise ratio varies between –3.5 dB and –20 dB, where the GNSS signal is deemed extremely weak.

V. I. Smetanin, I. M. Zhogin

Alex V. Conrad, Penina Axelrad, Bruce Haines et al.

This paper presents methods for the precise orbit determination (POD) of a satellite in the CYGNSS constellation based on available single-frequency GPS code and carrier measurements. The contributions include the development and evaluation of procedures for single-frequency POD with GipsyX, improvement of CYGNSS orbit knowledge, and an assessment of its final accuracy. Ionospheric effects are mitigated using the GRAPHIC processing method, and spacecraft multipath effects are calibrated with an azimuth/elevation-dependent antenna calibration map. The method is demonstrated using comparable data from the GRACE mission, from which we infer the expected accuracy of the CYGNSS results. Processing more than 170 days of data from each mission, a 1s CYGNSS orbit accuracy of 2.8 cm radial, 2.4 cm cross-track, and 6 cm in-track is demonstrated. We expect that achieving this level of performance will expand the set of future scientific investigations that can be undertaken using satellites equipped with single-frequency GNSS.

Jason Anderson, Sherman Lo, Andrew Neish et al.

Here we delineate a complete satellite-based augmentation system (SBAS) authentication scheme, including over-the-air rekeying (OTAR), that uses the elliptic curve digital signature algorithm (ECDSA) and timed efficient stream loss-tolerant authentication (TESLA) without the quadrature (Q) channel. This scheme appends two new message types to the SBAS scheduler without over-burdening the message schedule. We have taken special care to ensure that our scheme (1) meets the appropriate security requirements needed to prevent and deter spoofing; (2) is compatible with existing cryptographic standards; (3) is flexible, expandable, and future-proof to different cryptographic and implementation schemes; and (4) is backward compatible with legacy receivers. The scheme accommodates a diverse set of features, including authenticating core-constellation ephemerides. We discuss the SBAS provider and receiver machine state and its startup, including its use by aircraft that traverse differing SBAS coverage areas. We tested our scheme with existing SBAS simulation and analysis tools and found that it had negligible effects on current SBAS availability and continuity requirements.

Nacer Naciri, Sunil Bisnath

Global navigation satellite system (GNSS) precise point positioning (PPP) has potential as an alternative or replacement for real-time kinematic (RTK) processing. In this work, we reached for RTK levels of performance without the need for local information through PPP (i.e., centimeter-level positioning that was reached near-instantaneously). This work makes use of information currently available from processing signals from global positioning system (GPS), Galileo, BeiDou-2/3, and GLONASS by fixing ambiguities for the first three constellations on all available frequencies. This processing was done using a four-frequency, four-constellation uncombined decoupled clock model (DCM) that has been expanded as part of this work. The results were tested on 1448 global datasets and showed that instantaneous convergence on average to 2.5 cm error can be achieved for 81% of the stations. These findings were reinforced by the results of epoch-by-epoch processing, as an average of 80% of all single epochs converged below 2.5 cm error at 1s, as opposed to less than the 0.5% typically observed for classic PPP.

Ignacio Fernandez-Hernandez, Rui Hirokawa, Vincent Rijmen et al.

This paper analyzes candidate schemes for PPP/PPP-RTK (precise point positioning/real-time kinematic) data authentication. Asymmetric schemes are proposed based on existing standards and compatible with GNSS messages. Post-quantum cryptographic signatures are also reviewed and discussed. Two schemes are selected for analysis: digital signature (DS) based on ECDSA, and delayed disclosure (DD) based on a hybrid scheme using the TESLA protocol. Each of them is described in detail for both Galileo high-accuracy service and QZSS centimeter-level accuracy service. The performance of the schemes in terms of time to receive the corrections message and increase in the age of data (?AOD) is analyzed. The analysis is complemented by a review of the CPU consumption at receiver level.