Hasil untuk "Canals and inland navigation. Waterways"

Richard B. Langley

Welcome to the Spring 2025 issue of NAVIGATION. In this issue, we feature articles on a wide range of topics including jamming and spoofing of GNSS signals, navigation using pulsars, high accuracy positioning using a global differential GPS service, and the use of Starlink for positioning, navigation, and timing.

Ziao Liu, Shuai Zhao, Zhijian Hu et al.

Rotation modulation technology in inertial navigation systems (INS) can effectively suppress the divergence of navigation errors, thereby enhancing long-endurance navigation accuracy. However, established INS calibration methods do not fully account for non-orthogonality between the dual rotation axes, which may couple with other errors and degrade overall navigation performance. To address this issue, this paper develops a mathematical model that accounts for axis non-orthogonality and analyzes its effects on system behavior. Based on this model, the paper proposes a calibration scheme that mitigates the effect of non-orthogonality without the need for special alignment procedures. Simulation-based and experimental results demonstrate that the proposed approach effectively reduces attitude and velocity errors under both static and rotation modulation conditions. The proposed method thus represents a significant improvement in long-term navigation accuracy compared to traditional calibration methods.

Emile Ghizzo, Mathieu Hussong, Julien Lesouple et al.

In the context of global navigation satellite systems (GNSSs), synchronization is crucial for successfully decoding the navigation message and accurately estimating pseudoranges. Synchronization of each received GNSS signal typically involves at least two tracking loops: a delay lock loop (DLL) and a phase lock loop (PLL). The reception of a spoofed signal disrupts the synchronization process, potentially leading to erroneous pseudorange estimation or loss of service. This paper investigates the impact of spoofing on code, carrier phase, and frequency tracking estimates and proposes a transformation-based strategy to characterize the joint DLL and PLL under spoofing, focusing on the system’s stable equilibria (SE), linearity and interdependence, transient response, and noise impact. The study reveals the nonlinearity and interdependence of the tracking loops (i.e., the PLL and DLL cannot be considered separately) and shows the emergence of multiple SE, leading to potential chaotic behavior and bifurcation.

Mark Hartigan, E. Glenn Lightsey

Several organizations, including NASA and the European Space Agency, have initiated plans for establishing lunar navigation satellite systems (LNSSs). This effort is driven by surging interest in the Moon as a platform for scientific discovery and staging area for future missions beyond Earth orbit. Near-Earth missions benefit from GNSSs, which have been refined over decades and are capable of real-time, sub-meter level positioning. For GNSS systems, the navigation community and managing organizations, such as the U.S. Department of Defense (in the case of GPS), have precisely characterized the error sources inherent in pseudorange and range-rate measurements in Earth’s vicinity. Here, we draw parallels between errors in current GNSSs and those expected in future cislunar navigation systems. We identify key differences between the terrestrial and lunar environments and propose methods to accurately quantify the resulting measurement errors. Specifically, we develop techniques for constructing a time-varying error budget for pseudorange and pseudorange-rate measurements near the Moon and then test these techniques using arbitrary system and signal configurations.

Todd Ely, Zaid Towfic, Dana Sorensen

The Iris software radio has been updated to collect one-way Doppler and range data for potential use with deep space autonomous navigation. One-way radiometric data have found limited use because a typical radio oscillator is not sufficiently stable for use in navigation. However, Iris has been paired with a chip-scale atomic clock (CSAC) via an input signal of one pulse per second. With superior stability relative to a typical oscillator, the CSAC has the potential to provide onboard tracking data with sufficient accuracy to support a small satellite mission with modest navigation requirements. In this paper, we develop models of the Iris radio one-way Doppler and range data and analyze their performance in lab testing prior to a future inflight test on NASA’s CAPSTONE mission to the Moon. The test results confirm theoretical predictions for range precision measured between 0.38 m and 2.21 m with a range rate of 11 mm/s at 60 s.

Keidai Iiyama, Sriramya Bhamidipati, Grace Gao

There is a growing interest in the use of legacy terrestrial Global Positioning System (GPS) signals to determine the precise positioning and timing onboard a lunar satellite. Unlike prior works that utilize pseudoranges with meter-level accuracy, we propose a precise positioning and timekeeping technique that leverages carrier-phase measurements with millimeter-level accuracy (when integer ambiguities are correctly fixed). We design an extended Kalman filter framework that harnesses the intermittently available terrestrial GPS time-differenced carrier-phase (TDCP) values and gravitational accelerations predicted by the orbital filter. To estimate the process noise covariance, we implement an adaptive state noise compensation algorithm that adapts to the challenging lunar environment with weak gravity and strong third-body perturbations. Additionally, we perform measurement residual analysis to discard TDCP measurements corrupted by cycle slips and increased measurement noise. We present Monte-Carlo simulations of a lunar satellite in an elliptical lunar frozen orbit and quasi-frozen low lunar orbit, wherein we showcase higher positioning and timing accuracy as compared with the pseudorange-only navigation solution.

Ryan S. Cassel

Many common discriminators used for code tracking of global navigation satellite system (GNSS) signals are ratios of quadratic forms of the correlation outputs. Here we derive a general expression for the gain of this type of discriminator and show that it depends on the effective carrier-to-noise ratio. We then evaluate this expression for several different code discriminators and GNSS signals, including GPS C/A-code, P-code, L1C, and M-code, Galileo E1 OS, GLONASS L1OF and L2OF, and BeiDou B1I and B2I. We also determine how noise and interference saturate the discriminator (i.e., make its output less sensitive to changes in the input) and the resulting effect on loop bandwidth. The discriminator gains described in this paper compensate for the saturation and ensure that loop bandwidth and code tracking performance can be accurately predicted and controlled over a critical range of effective carrier-to-noise ratios.

Jyh-Ching Juang

In the multi-GNSS era, the observable satellites are more than needed and the benefit of processing more than enough satellites is marginal. It is thus desired to select a subset of satellites so that the receiver operation complexity and navigation performance can be balanced. In the paper, performance requirements in navigation accuracy and integrity are represented in terms of a performance index and the performance-based satellite selection is to determine the satellite combination to minimize the performance index. A linear matrix inequality (LMI) relaxation approach is developed to solve the problem and render candidates of satellites. The proposed approach quantifies the significance of each satellite on the resulting performance metric and, more importantly, provides a lower bound in satellite selection for performance-based navigation. The generalizations of the proposed approach in multi-epoch satellite selection is also discussed. Examples are provided to illustrate the effectiveness of the proposed approach.

Jacek Stefanski, Jaroslaw Sadowski

This paper proposes an object location method for all types of applications, including the Internet of Things. The proposed method enables estimations of the position and orientation of an object on a plane or in space, especially during motion, by means of location signals transmitted simultaneously from two transmitters placed on the object at a known distance from each other. A mathematical analysis of the proposed method and Newton’s algorithm for solving the system of nonlinear positional equations is presented. Next, an analysis of a position-dilution-of-precision parameter for the proposed method and a Cramer–Rao lower bound, limiting the accuracy of the method, is presented. Finally, the results of complex simulation studies on the efficiency of the proposed method are described.

Jessica Belzer, Frank van Graas

Self-interference can cause large errors of up to tens of meters on the GPS C/A code pseudorange measurement. Although the probability of an occurrence of large self-interference errors is small, to enable the use of C/A code phase measurements in high accuracy or safety-of-life applications, a detection or mitigation method is needed. A stressful case of self-interference is modeled on a GPS hardware simulator to investigate monitor performance using real signal results. A summary of contributions in this paper follows. Self-interference pseudorange error characteristics within and mitigation requirements for the Ground Based Augmentation System (GBAS) Approach Service Type D (GAST-D) environment are identified. Existing monitors are evaluated for their response to self-interference and their ability to detect the error based on the GAST-D environment. This includes the potential for misidentification of the error. A novel Frequency Domain Cross-Correlation (FDCC) detector is proposed that can uniquely identify self-interference error with no siting constraints.

Jinsil Lee, Minchan Kim, Dongchan Min et al.

This study introduces a navigation integrity and continuity algorithm against an inertial measurement unit (IMU) sensor fault within a Kalman filter (KF) that ensures a high level of safety for IMU-integrated safety-critical navigation applications. A representative example of an IMU integrated navigation system is a global navigation satellite system (GNSS)/IMU system. Most previous studies have focused on GNSS faults when evaluating the integrity and continuity of a KF-based GNSS/IMU navigation system, leaving the IMU fault hypothesis unaddressed. Unlike GNSS, which is applied in the measurement update step within the KF, IMU measurements are applied in the state prediction step, which results in different fault propagation characteristics in the user state error compared with those in GNSS. This paper analytically derives the sequential IMU fault impacts on user state errors. Based on this investigation, a KF innovation-based fault detector and protection-level equations are developed, which can safely bound user state errors against sequential IMU fault impacts.

Amira Ghennaï, Said Madani, Carola Hein

Sustainable development projects require careful balancing of economic interests and ecological needs. The case of Skikda, a city in northeast Algeria, located on the Mediterranean coast, illustrates the challenges connected with such a development. The ancient city coexists with a young hydrocarbon port and industrial pole that serves as a transfer hub in the flow of petroleum between hinterland and sea. The installation of the port and petrochemical refining plants on the banks of the estuary of the Safsaf River presents many challenges to local citizens and the ecosystem, including pollution of the water system, groundwater, and river water, and damage to the area’s ancient heritage. This study argues that we need new and less polluting forms of intermodality between hinterland and seaport to make urban mobility more sustainable. It asks whether and how the existing rivers and wadis (river channels that are dry except during rainy periods) can be transformed into artificial canals for river navigation to improve the transport fluidity and sustainability of Skikda. To answer this question, the study adopts a prospective approach using the MICMAC scenario method. This approach entails, first, presenting and evaluating the potentialities of the existing rivers of Skikda using QGIS, and second, discussing and proposing scenarios for transforming these rivers into urban waterways, that is, artificial canals for inland navigation. The prospect of inland waterway transport in Skikda may be a radical scenario, yet, despite its hydraulic capacity and advantages, this system is not receiving attention in Algeria. We suggest that water transport can breathe sustainable blue life into a vulnerable industrial port city, transforming its challenges into opportunities.

Nesreen I. Ziedan

The positioning accuracy of global navigation satellite system receivers is frequently degraded in urban areas due to reflected signals. A moving receiver faces additional challenges because it needs to adjust to changes in the statuses of the signals received, including line-of-sight (LOS), multipath, non-LOS, or invisible. This paper proposes two new algorithms that can be used to enhance the accuracy of a moving receiver. The first algorithm is called Optimized Position Estimation (OPE). The OPE algorithm estimates the most likely paths and identifies the one with the optimal weight. The second algorithm is called Intelligent Signal Status Estimation (ISE). The ISE algorithm utilizes a self-organizing map machine-learning algorithm to estimate the probability of a change in signal status. The algorithms are tested using global positioning system C/A signals, which have over 50 changes in their statuses. The results obtained using these algorithms reveal that the accuracy is enhanced by as much as 96.3% (i.e., a 27-fold improvement) when compared to results using a conventional navigation algorithm.

Mark B. Hinga, Dale A. Williams

Autonomous cislunar spacecraft navigation is critical to mission success as communication to ground stations and access to global positioning system (GPS) signals could be lost. However, if the satellite has a camera of sufficient quality, geometric line-of-sight (unit vector) measurements can be made to known lunar landmarks (e.g., Tycho Crater) to provide observations that enable autonomous estimation of the position and velocity of the spacecraft. In this study, an improved batch gaussian initial orbit determination (IOD) differential corrector (DC) algorithm, based on the approximated values of the two-body f and g series, is applied to initialize a (non-conic based) circular restricted three body problem (CR3BP) extended Kalman Filter (EKF) navigator. This navigator collects geometric line-of-sight unit vector (angle only) measurements to a known location on the Moon to sequentially estimate the position and velocity of an observer spacecraft flying on an approximate southern L1 Halo orbit. In this study, it was found that the best approach is to initialize the CR3BP EKF (navigator) using the solution from the batch DC filter with at least 10 measurements taken against the perceived centroid of Tycho Crater. Thereafter, it is best to continue the navigator with subsequent measurements taken against the same center coordinates of the Tycho Crater, where these coordinates are now expressed in the CR3BP rotating frame. For successful conic-based batch filter initialization and long-term CR3BP EKF convergence, it was found that the cadence for all optical measurements should be taken at 10 minutes for a simulated measurement noise of 0.1° one sigma uncertainty about the line-of-sight measurement unit vector.

Sriramya Bhamidipati, Tara Mina, Alana Sanchez et al.

There has been a growing interest in using small satellites (SmallSats) for a future lunar navigation and communication satellite system (LNCSS). We conceptualize the design of a SmallSat-based LNCSS with Earth-global positioning system (GPS) time transfer that provides navigation and communication services near the lunar south pole. A hybrid constellation design is formulated, wherein all satellites provide navigation services while only a fraction are communication-enabled. Using Systems Tool Kit software, we examine various LNCSS case studies based on an elliptical lunar frozen orbit with a lower-grade chip-scale atomic clock. Case studies are evaluated in terms of (1) navigation considerations, including position and timing accuracy, lunar user equivalent ranging error, and dilution of precision, (2) communication considerations, including data volume, availability, and data rate, and (3) SmallSat factors, including cost, size, weight, and power. We performed a trade-off analysis for satisfying the criteria outlined by international space agencies while designing low-cost, low-SWaP lunar constellations.

Cheng Liu, Shuai Xiong, Yongchao Geng et al.

Because of the high complementarity between global navigation satellite systems (GNSSs) and visual-inertial odometry (VIO), integrated GNSS-VIO navigation technology has been the subject of increased attention in recent years. In this paper, we propose an embedded high-precision multi-sensor fusion suite that includes a multi-frequency and multi-constellation GNSS module, a consumption-grade inertial measurement unit (IMU), and a grayscale camera. The suite uses an NVIDIA Jetson Xavier NX as the host and develops a Field Programmable Gate Array-based controller for hardware time synchronization between heterogeneous sensors. A multi-state constraint Kalman filter is used to generate the tightly-coupled estimation from the camera and the IMU. As a result, the GNSS output is loosely coupled to facilitate the acquisition of the global drift-free estimation. Results from the calibration reveal that the time synchronization accuracy of the suite is better than 30 µs (standard deviation [STD]) and that the projection error of camera-IMU is less than 0.1 pixels (STD); these results highlight the advantage of this hardware time synchronization mechanism. Results from the vehicle-mounted tests reveal reductions in the three-dimensional (3D) positioning error from 8.455 m to 5.751 m (root mean square) on experimental urban roads, which significantly improves the accuracy and continuity of GNSS individual positioning. In underground sites where the satellite signal is completely unavailable, the 3D position error drift of the suite is only 1.58 ‰, which also shows excellent performance.

Cillian O’Driscoll, Ignacio Fernández-Hernández

This paper investigates the distribution of unpredictable symbols in the open service navigation message authentication (OSNMA) scheme, which introduces cryptographic elements into the Galileo I/NAV message. Prior work has described the forward estimation attack (FEA; Curran & O’Driscoll, 2016), that takes advantage of the forward error correction (FEC) employed by the Galileo E1 OS to ensure that a spoofed receiver correctly decodes the I/NAV message, even if it has been generated with errors in some symbols. In order to defend against such an attack, the receiver can re-encode the navigation message into symbols and compare the symbol error rates for those symbols that are predictable and those that are not. In order to perform this, it is first necessary to know which symbols are unpredictable. This paper presents in detail how this can be achieved, including the impact of the cyclic redundancy check (CRC) on symbol unpredictability.

Ilija Jovanovic, John Enright

Planetary rover navigation frequently relies on dead reckoning and external infrastructure such as orbiting satellites. Celestial navigation techniques combine measurements of the Sun, stars, and gravity to provide autonomous absolute localization. This study examines the performance of digital star sextants (DSS)—a suite of sensors combining a star tracker and an inclinometer—on estimating position on the planetary surface. In particular, we discuss the estimation, calibration, and error analysis for an elevation-only measurement formulation that does not rely on ground-truth heading information. Field tests and Monte Carlo simulations provide validation of the proposed techniques. The real-world performance of the experimental system gives a mean single-orientation error of 296 m. The relative agreement between the predicted and observed error reveals a clear roadmap to help evaluate the impact of prospective sensor improvements on DSS performance.

Tara Yasmin Mina, Grace Xingxin Gao

With the birth of the next-generation GPS III constellation and the upcoming launch of the Navigation Technology Satellite-3 (NTS-3) testing platform to explore future technologies for GPS, we are indeed entering a new era of satellite navigation. Correspondingly, it is time to revisit the design methods of the GPS spreading code families. In this work, we develop a natural evolution strategy (NES) machine-learning algorithm with a Gaussian proposal distribution which constructs high-quality families of spreading code sequences. We minimize the maximum between the mean-squared auto-correlation and the mean-squared cross-correlation and demonstrate the ability of our algorithm to achieve better performance than well-chosen families of equal-length Gold codes and Weil codes, for sequences of up to length-1023 and length-1031 bits and family sizes of up to 31 codes. Furthermore, we compare our algorithm with an analogous genetic algorithm implementation assigned the same code evaluation metric. To the best of the authors’ knowledge, this is the first work to explore using a machine-learning approach for designing navigation spreading code sequences.

Timothy Needham, Michael Braasch

Safety certification of GNSS-aided inertial navigation systems (INS) in civil aircraft requires thorough testing to ensure proper operation, even in worst-case conditions. One error that must be considered is that of gravity compensation on accelerometer measurements. Prior to the work described in this paper, no stochastic models existed with the Gaussian bounding of the tails required to ensure integrity performance. This paper describes a method to determine efficient stochastic models of the error of current high-order gravity models such as EGM2008. The stochastic and high-order models are combined to achieve a high-fidelity model suitable for use in testing systems designed for low-approach operations such as RNP-AR. This paper also describes a method to determine efficient stochastic models for low-order gravity models such as the WGS-84 ellipsoidal model. Such models may be used in testing systems designed for operations with less stringent lateral requirements.