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Positioning systems are integral to Unmanned Underwater Vehicle (UUV) operation, enabling precise navigation and control in complex underwater environments. This paper comprehensively reviews the key technologies employed for UUV positioning, including acoustic systems, inertial navigation, Doppler velocity logs, and GPS when near the surface. These systems are essential for seabed mapping, marine infrastructure inspection, and search and rescue operations. The review highlights recent technological advancements and examines the integration of these systems to enhance accuracy and operational efficiency. It also addresses ongoing challenges, such as communication constraints, environmental variability, and discrepancies between theoretical models and field applications. Future trends in positioning system development are discussed, with a focus on improving reliability and performance in diverse underwater conditions to support the expanding capabilities of UUVs across scientific, commercial, and rescue missions. [ABSTRACT FROM AUTHOR]

Fishing impacts the marine environment significantly, and quantifying this impact requires precise fishing effort data. This study explores the challenges associated with accurately estimating fishing effort by purse seiners and proposes a solution using records collected from real-time communication devices on fishing fleets. The estimation of fishing effort based on high-frequency GPS data can be verified with the onboard visual records. Additionally, by linking vessels within a fleet, the method utilizes information from carriers (vessels that transport fish) to enhance the estimation. Through the use of generalized additive models, this study effectively estimates the fishing effort of Japanese purse seiners, demonstrating their accuracy. Furthermore, by incorporating carrier information, models based on matched records prove to have superior predictive performance compared to those based on fishing vessel or carrier records alone. These findings lay the foundation for the potential of this approach to provide precise and cost-effective information for sustainable fishery management. The affordability of GPS devices and the common requirement of communication devices across various fleets further support the feasibility of implementing this approach. [ABSTRACT FROM AUTHOR]

UCO DWM1001 is a free software developed to facilitate the work with DWM1001-DEV, one of the most widely used ultra-wideband (UWB) development boards. The software is designed to process, display, and store the relevant information of a UWB network system. The developed tool enables the user to manage the device transparently, establishing a connection, managing communication, and providing a range of features that facilitate the work and study of UWB technology. Communication is based on terminal emulation, whereby received messages are processed in accordance with their properties, the operating mode set, or the application tool used. The software's principal functions comprise real-time data visualisation, data saving, and an integrated terminal emulator for direct communication with the DWM1001-DEV development board. The tool, developed using the Qt framework, is intended to provide researchers with a straightforward method to utilise and assess the performance of DWM1001-DEV in diverse indoor settings, as well as to construct a basic UWB positioning network. Two illustrative examples are presented to demonstrate the capabilities of UCO DWM1001 software.

Positioning systems are integral to Unmanned Underwater Vehicle (UUV) operation, enabling precise navigation and control in complex underwater environments. This paper comprehensively reviews the key technologies employed for UUV positioning, including acoustic systems, inertial navigation, Doppler velocity logs, and GPS when near the surface. These systems are essential for seabed mapping, marine infrastructure inspection, and search and rescue operations. The review highlights recent technological advancements and examines the integration of these systems to enhance accuracy and operational efficiency. It also addresses ongoing challenges, such as communication constraints, environmental variability, and discrepancies between theoretical models and field applications. Future trends in positioning system development are discussed, with a focus on improving reliability and performance in diverse underwater conditions to support the expanding capabilities of UUVs across scientific, commercial, and rescue missions.

A software- and hardware-based monitoring system has been developed for metallic components, on the basis of eddy current scanning of nonmagnetic materials. Design details are presented. Experimental results confirm that this system may be used to monitor metallic nanofilms. [ABSTRACT FROM AUTHOR]

Indoor device-free localization systems utilizing received signal strength indicator (RSSI) have become mainstream because of their low pricing, low complexity, low effort, low energy, and the framework can be reusable. However, it is reviewed from the existing literature that for paying extra attention to positioning errors mitigation, researchers fail to meet the optimum characteristics requirement for measurements. To overcome such limitations and focus on current challenges in measurements, this article proposes an RSSI fingerprinting positioning algorithm using the K-nearest neighborhood and regression analysis technique such that the localization precisions can be improved. Meanwhile, to get higher location accuracy, some special RSSI values are compared to obtain a suitable one. In the proposed positioning scheme, the indoor site is divided into two parts. Moreover, in each part, the positions of a smartphone at different reference points are localized with at most two access points (APs). This strategy not only reduces the neighboring noises significantly caused by the surrounding wireless signals coming from other electronic devices but also reduces the system management overhead due to the use of a minimum number of APs, which increases the system's ability. The performance shows that the proposed scheme is highly capable of increasing the users' experience and could be a research direction for future positioning systems. [ABSTRACT FROM AUTHOR]

Intelligent Transportation Systems (ITSs) technology has advanced during the past years, and it is now used for several applications that require vehicles to exchange real-time data, such as in traffic information management. Traditionally, road traffic information has been collected using on-site sensors. However, crowd-sourcing traffic information from onboard sensors or smartphones has become a viable alternative. State-of-the-art solutions currently follow a centralized model where only the service provider has complete access to the collected traffic data and represent a single point of failure and trust. In this paper, we propose GOLIATH, a blockchain-based decentralized framework that runs on the In-Vehicle Infotainment (IVI) system to collect real-time information exchanged between the network’s participants. Our approach mitigates the limitations of existing crowd-sourcing centralized solutions by guaranteeing trusted information collection and exchange, fully exploiting the intrinsic distributed nature of vehicles. We demonstrate its feasibility in the context of vehicle positioning and traffic information management. Each vehicle participating in the decentralized network shares its position and neighbors’ ones in the form of a transaction recorded on the ledger, which uses a novel consensus mechanism to validate it. We design the consensus mechanism resilient against a realistic set of adversaries that aim to tamper or disable the communication. We evaluate the proposed framework in a simulated (but realistic) environment, which considers different threats and allows showing its robustness and safety properties. [ABSTRACT FROM AUTHOR]

This brief presents a novel one-step adaptive parameter estimation framework for identification of unknown asymmetric dead-zone characteristic parameters (e.g., width and slopes) in the sandwich systems, which avoids using the intermediate variables or carrying out a two-step recursive identification procedure. By applying a continuous piecewise linear neural network (CPLNN), the asymmetric dead-zone nonlinearities can be represented into a parameterized form, where the dead-zone characteristic parameters can be derived based on the online updated CPLNN weights. Moreover, after representing the sandwich system into an augmented system, an adaptive observer is designed to reconstruct the immeasurable internal variables, and an adaptive law with guaranteed convergence is used to online update the CPLNN weights so as to estimate the dead-zone parameters. In this adaptive law, the parameter estimation error information is extracted using simple filters and introducing several auxiliary variables. It is proven that the observation error and estimation error both converge to a small set around zero. The efficiency of the estimation method is exemplified via practical experiments on an $X$ - $Y$ positioning platform. [ABSTRACT FROM AUTHOR]

This two-part paper aims to provide a comprehensive survey on how emerging technologies, e.g., wireless and networking, artificial intelligence (AI) can enable, encourage, and even enforce social distancing practice. In Part I, an extensive background of social distancing is provided, and enabling wireless technologies are thoroughly surveyed. In this Part II, emerging technologies such as machine learning, computer vision, thermal, ultrasound, etc., are introduced. These technologies open many new solutions and directions to deal with problems in social distancing, e.g., symptom prediction, detection and monitoring quarantined people, and contact tracing. Finally, we discuss open issues and challenges (e.g., privacy-preserving, scheduling, and incentive mechanisms) in implementing social distancing in practice. As an example, instead of reacting with ad-hoc responses to COVID-19-like pandemics in the future, smart infrastructures (e.g., next-generation wireless systems like 6G, smart home/building, smart city, intelligent transportation systems) should incorporate a pandemic mode in their standard architectures/designs.

Social distancing plays a pivotal role in preventing the spread of viral diseases illnesses such as COVID-19. By minimizing the close physical contact among people, we can reduce the chances of catching the virus and spreading it across the community. This two-part paper aims to provide a comprehensive survey on how emerging technologies, e.g., wireless and networking, artificial intelligence (AI) can enable, encourage, and even enforce social distancing practice. In this Part I, we provide a comprehensive background of social distancing including basic concepts, measurements, models, and propose various practical social distancing scenarios. We then discuss enabling wireless technologies which are especially effect- in social distancing, e.g., symptom prediction, detection and monitoring quarantined people, and contact tracing. The companion paper Part II surveys other emerging and related technologies, such as machine learning, computer vision, thermal, ultrasound, etc., and discusses open issues and challenges (e.g., privacy-preserving, scheduling, and incentive mechanisms) in implementing social distancing in practice.

The paper presents the methods and results of an experimental study that highlights the behavior of a pneumatic actuator under different pressures and with different loads applied. One important challenge that occurs in the application of pneumatic muscles is the phenomenon of hysteresis, which causes a nonlinear relationship between the input–output values. The aim of this study is to identify the occurrence of hysteresis in the operation of a small pneumatic muscle in different conditions. Thus, different loads are attached to the free end of a pneumatic muscle and different successive pressures are applied in order to examine the hysteresis of the contraction ratio when the muscle is inflated and then deflated. The obtained equations that describe the relationship between the input pressure and the axial contraction are significant for reaching a high-performance position control. In this regard, the article proposes a solution to increase positioning accuracy based on pressure control using a proportional pressure regulator and a programmable logic controller. [ABSTRACT FROM AUTHOR]

With the advent of the Internet of Things (IoT) and ubiquitous presence of sensor nodes, positioning technologies have become a topic of interest among researchers. While the applications of positioning systems are very vast, determining the position of moving sensor nodes, finding missing people in large areas, and object tracking are among the most popular ones. The focus of this paper is to propose a positioning system to locate missing people in theme parks. Currently, radio frequency identification (RFID) systems are used in modern theme parks to locate lost visitors. In these systems, a wristband with active RFID tag is given to each visitor and RFID readers are deployed in predetermined locations. When a visitor is in the communication range of a reader, its location can be estimated based on the location of the reader. Therefore, the accuracy of these systems is relevant to the communication range of readers. Another limitation of RFID-based systems is due to the fact that readers cannot be placed in communication range of each other as they can interference with each other. It is clear that the only way to increase the accuracy of such systems is by increasing the number of readers and decreasing the communication range of each reader. In this paper, a Bluetooth low energy (BLE)-based system is proposed to be used in theme parks for locating lost visitors. The advantage of using BLE is due to the fact that it uses frequency hopping spread spectrum (FHSS) thus readers can be placed in communication range of each other without severe interference. In the proposed method, at first, the optimal places for deploying readers are obtained using ant colony optimization (ACO). Then, a fuzzy approach is used to increase the accuracy of the system. Three different signal levels are defined to be used in our fuzzy system based on which the location of visitors can be estimated. By using three levels of signal strength, the accuracy of the system is increased compared with the similar system with the similar number of readers. The simulation results show that the accuracy of the system is improved using this method, and the cost of the system is decreased as BLE readers are much less expensive than their RFID counterparts. [ABSTRACT FROM AUTHOR]

Positioning systems based on the lateration method utilize distance measurements and the knowledge of the location of the beacons to estimate the position of the target object. Although most of the global positioning techniques rely on beacons whose locations are known a priori, miscellaneous factors and disturbances such as obstacles, reflections, signal propagation speed, the orientation of antennas, measurement offsets of the beacons hardware, electromagnetic noise, or delays can affect the measurement accuracy. In this paper, we propose a novel hybrid calibration method based on Neural Networks (NN) and Apparent Beacon Position Estimation (ABPE) to improve the accuracy of a lateration positioning system. The main idea of the proposed method is to use a two-step position correction pipeline that first performs the ABPE step to estimate the perceived positions of the beacons that are used in the standard position estimation algorithm and then corrects these initial estimates by filtering them with a multi-layer feed-forward neural network in the second step. In order to find an optimal neural network, 16 NN architectures with 10 learning algorithms and 12 different activation functions for hidden layers were implemented and tested in the MATLAB environment. The best training outcomes for NNs were then employed in two real-world indoor scenarios: without and with obstacles. With the aim to validate the proposed methodology in a scenario where a fast set-up of the system is desired, we tested eight different uniform sampling patterns to establish the influence of the number of the training samples on the accuracy of the system. The experimental results show that the proposed hybrid NN-ABPE method can achieve a high level of accuracy even in scenarios when a small number of calibration reference points are measured.

The paper presents the methods and results of an experimental study that highlights the behavior of a pneumatic actuator under different pressures and with different loads applied. One important challenge that occurs in the application of pneumatic muscles is the phenomenon of hysteresis, which causes a nonlinear relationship between the input–output values. The aim of this study is to identify the occurrence of hysteresis in the operation of a small pneumatic muscle in different conditions. Thus, different loads are attached to the free end of a pneumatic muscle and different successive pressures are applied in order to examine the hysteresis of the contraction ratio when the muscle is inflated and then deflated. The obtained equations that describe the relationship between the input pressure and the axial contraction are significant for reaching a high-performance position control. In this regard, the article proposes a solution to increase positioning accuracy based on pressure control using a proportional pressure regulator and a programmable logic controller.

Мета роботи. Розробка динамічної макромоделі крокового двигуна (КД) для задач дослідження систем позиціювання та інших робототехнічних мехатронних систем в програмах автоматизованого проектування для електроніки (ЕCAD), яка відповідає критеріям економічності та надійності. Методи дослідження. Моделінг КД здійснено на базі поведінкових елементів з бібліотеки ЕCAD, модель системи позиціювання отримано в термінах теорії автоматичного управління у вигляді сполучення ланок, передаточні функції для яких отримані як функції часу. Для ефективного моделювання (симуляції) подібних САУ на основі акаузального по суті математичного апарату ЕCAD, моделям надано ознаки каузальності за допомогою залежних джерел, керованих напругою. Об’єктом дослідження є процес моделювання автоматизованих систем із КД в якості актуаторів в середовищі ЕCAD, предметом дослідження є моделі КД. Отримані результати. На основі аналізу областей адекватності та математичного апарату існуючих моделей КД, сформовані критерії для розробки економічної моделі, придатної для адекватного макромоделювання САУ із КД в середовищі ЕCAD. Розроблено мінімальну модель КД, яку досліджено для встановленого режиму в навантаженому стані. В ході апробації та верифікації шляхом моделювання підсистеми позиціювання автоматизованої системи визначення поверхневого потенціалу, встановлено, що модель забезпечує високу швидкість та алгоритмічну надійність симуляції при високій точності результатів аналізу динамічних характеристик. Макромодель інстальовано в бібліотеку програми Micro Cap 11. Наукова новизна. Нова макромодель КД, яка відповідає критеріям адекватності, надійності та економічності, синтезована на основі нового підходу у моделінгу об’єктів на макрорівні, який поєднує принципи побудови структур та ланок САУ згідно теорії автоматичного управління (ТАУ) із можливостями поведінкового моделювання в середовищі програм автоматизованого проектування в електроніці (ЕCAD). Передаточні функції для таких моделей будуються як функції часу, без переходу в комплексну площину, що дозволяє розширити область їхньої адекватності, порівняно із класичними моделями. Такі макромоделі дозволяють досліджувати динамічні режими в автоматизованих системах позиціювання. Практична цінність. Макромодель КД розширює математичне забезпечення ЕCAD, знижує імовірність появи алгоритмічних збоїв та прискорює моделювання САУ в ЕCAD. Використаний при її синтезі підхід дозволяє будувати аналогічні моделі для іншого програмного забезпечення (CAS, CAE)

This study explores whether positioning systems are a viable alternative to timing gates when it comes to measuring sprint times in ice hockey. We compared the results of a single-beam timing gate (Brower Timing) with the results of the Iceberg optical positioning system (Optical) and two radio-based positioning systems provided by InMotio (Radio 1) and Kinexon (Radio 2). The testing protocol consisted of two 40 m linear sprints, where we measured sprint times for a 11 m subsection (Linear Sprint 11), and a shuttle run (Shuttle Total), including five 14 m sprints. The exercises were performed by six top-level U19 field players in regular ice hockey equipment on ice. We quantified the difference between measured sprint times e.g., by Mean Absolute Error (MAE) (s) and Intra Class Correlation (ICC). The usefulness of positioning systems was evaluated by using a Coefficient of Usefulness (CU), which was defined as the quotient of the Smallest Worthwhile Change (SWC) divided by the Typical Error (both in s). Results showed that radio-based systems had a higher accuracy compared to the optical system. This concerned Linear Sprint 11 (MAEOptical = 0.16, MAERadio1 = 0.01, MAERadio2 = 0.01, ICCOptical = 0.38, ICCRadio1 = 0.98, ICCRadio2 = 0.99) as well as Shuttle Total (MAEOptical = 0.07, MAERadio1 = 0.02, MAERadio2 = 0.02, ICCOptical = 0.99; ICCRadio1 = 1.0, ICCRadio2 = 1.0). In Shuttle Total, all systems were able to measure a SWC of 0.10 s with a probability of >99% in a single trial (CUOptical = 4.6, CURadio1 = 6.5, CURadio2 = 5.1). In Linear Sprint 11 an SWC of 0.01 s might have been masked or erroneously detected where there were none due to measurement noise (CUOptical = 0.6, CURadio1 = 1.0, CURadio2 = 1.0). Similar results were found for the turning subsection of the shuttle run (CUOptical = 0.6, CURadio1 = 0.5, CURadio2 = 0.5). All systems were able to detect an SWC higher than 0.04 s with a probability of at least 75%. We conclude that the tested positioning systems may in fact offer a workable alternative to timing gates for measuring sprints times in ice hockey over long distances like shuttle runs. Limitations occur when testing changes/differences in performance over very short distances like an 11 m sprint, or when intermediate times are taken immediately after considerable changes of direction or speed.

This study explores whether positioning systems are a viable alternative to timing gates when it comes to measuring sprint times in ice hockey. We compared the results of a single-beam timing gate (Brower Timing) with the results of the Iceberg optical positioning system (Optical) and two radio-based positioning systems provided by InMotio (Radio 1) and Kinexon (Radio 2). The testing protocol consisted of two 40 m linear sprints, where we measured sprint times for a 11 m subsection (Linear Sprint 11), and a shuttle run (Shuttle Total), including five 14 m sprints. The exercises were performed by six top-level U19 field players in regular ice hockey equipment on ice. We quantified the difference between measured sprint times e.g., by Mean Absolute Error (MAE) (s) and Intra Class Correlation (ICC). The usefulness of positioning systems was evaluated by using a Coefficient of Usefulness (CU), which was defined as the quotient of the Smallest Worthwhile Change (SWC) divided by the Typical Error (both in s). Results showed that radio-based systems had a higher accuracy compared to the optical system. This concerned Linear Sprint 11 (MAEOptical = 0.16, MAERadio1 = 0.01, MAERadio2 = 0.01, ICCOptical = 0.38, ICCRadio1 = 0.98, ICCRadio2 = 0.99) as well as Shuttle Total (MAEOptical = 0.07, MAERadio1 = 0.02, MAERadio2 = 0.02, ICCOptical = 0.99; ICCRadio1 = 1.0, ICCRadio2 = 1.0). In Shuttle Total, all systems were able to measure a SWC of 0.10 s with a probability of >99% in a single trial (CUOptical = 4.6, CURadio1 = 6.5, CURadio2 = 5.1). In Linear Sprint 11 an SWC of 0.01 s might have been masked or erroneously detected where there were none due to measurement noise (CUOptical = 0.6, CURadio1 = 1.0, CURadio2 = 1.0). Similar results were found for the turning subsection of the shuttle run (CUOptical = 0.6, CURadio1 = 0.5, CURadio2 = 0.5). All systems were able to detect an SWC higher than 0.04 s with a probability of at least 75%. We conclude that the tested positioning systems may in fact offer a workable alternative to timing gates for measuring sprints times in ice hockey over long distances like shuttle runs. Limitations occur when testing changes/differences in performance over very short distances like an 11 m sprint, or when intermediate times are taken immediately after considerable changes of direction or speed. [ABSTRACT FROM AUTHOR]

In underwater localization systems several sources of error may impact in different ways the accuracy of the final position estimates. Through simulations and statistical analysis it is possible to identify and characterize such sources of error and their relative importance. This is especially of use when an accurate localization system has to be designed within required accuracy prescriptions. This approach allows one to also investigate how much these sources of error influence the final position estimates achieved by an Extended Kalman Filter (EKF). This paper presents the results of experiments designed in a virtual environment used to simulate real acoustic underwater localization systems. The paper intends to analyze the main parameters that significantly influence the position estimates achieved by a Short Baseline (SBL) system. Specifically, the results of this analysis are presented for a proprietary localization system constituted by a surface platform equipped with four acoustic transducers used for the localization of an underwater target. The simulator here presented has the purpose of simulating the hardware system and modifying some of its design parameters, such as the base-line length and the errors on the GPS and Inertial Measurement Unit (IMU) units, in order to understand which parameters have to modify for improving the accuracy of the entire positioning system. It is shown that statistical analysis techniques can be of help in determining the best values of these parameters that permit to improve the performance of a real hardware system.

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Copyright of Technical Transactions / Czasopismo Techniczne is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the Third-Generation Partnership Project (3GPP) Long-Term Evolution (LTE) specifications, several 2-D positioning methods have been proposed to support location-based services (LBSs). It has been shown that the observed time difference of arrival (OTDOA) method provides the best result. With the advent of the fifth-generation cellular systems, 3-D beamforming will be introduced, and 2-D positioning may not be sufficient for future applications. Although the conventional OTDOA method can be used in 3-D positioning, it requires more base stations (BSs) in cooperation and often performs poorly in typical cellular network geometry. In this paper, we propose a novel OTDOA-based method to solve the problems. First, we exploit the sparsity of the wireless channel and propose to use a compressive-sampling-based channel estimation method, which greatly enhances the precision of time-of-arrival (TOA) estimation. Then, we propose a transmit beamforming scheme such that the elevation angle of departure (AOD) can be accurately estimated. Finally, we combine the estimated TOAs and the AOD in the OTDOA scheme to conduct 3-D positioning. With the proposed scheme, the number of BSs required for 3-D positioning remains the same as that of 2-D, and the positioning accuracy greatly outperforms that of the conventional OTDOA method. Simulations show that 90% of the position error can be less than 7 m. [ABSTRACT FROM PUBLISHER]

This paper presents an improved propagation channel model for the visible light in indoor environments. We employ this model to derive an enhanced positioning algorithm using on the relation between the time-of-arrivals (TOAs) and the distances for two cases either by assuming known or unknown transmitter and receiver vertical distances. We propose two estimators, namely the maximum likelihood estimator and an estimator by employing the method of moments. To have an evaluation basis for these methods, we calculate the Cramer-Rao lower bound (CRLB) for the performance of the estimations. We show that the proposed model and estimations result in a superior performance in positioning when the transmitter and receiver are perfectly synchronized in comparison to the existing state-of-the-art counterparts. Moreover, the corresponding CRLB of the proposed model represents almost about 20 dB reduction in the localization error bound in comparison with the previous model for some practical scenarios. [ABSTRACT FROM AUTHOR]

The problem of determining the optimal geometric configuration of a sensor network that will maximize the range-related information available for multiple target positioning is of key importance in a multitude of application scenarios. In this paper, a set of sensors that measures the distances between the targets and each of the receivers is considered, assuming that the range measurements are corrupted by white Gaussian noise, in order to search for the formation that maximizes the accuracy of the target estimates. Using tools from estimation theory and convex optimization, the problem is converted into that of maximizing, by proper choice of the sensor positions, a convex combination of the logarithms of the determinants of the Fisher Information Matrices corresponding to each of the targets in order to determine the sensor configuration that yields the minimum possible covariance of any unbiased target estimator. Analytical and numerical solutions are well defined and it is shown that the optimal configuration of the sensors depends explicitly on the constraints imposed on the sensor configuration, the target positions, and the probabilistic distributions that define the prior uncertainty in each of the target positions. Simulation examples illustrate the key results derived.

In this paper, we address the problem of determining the optimal geometric configuration of an acoustic sensor network that will maximize the angle-related information available for underwater target positioning. In the set-up adopted, a set of autonomous vehicles carries a network of acoustic units that measure the elevation and azimuth angles between a target and each of the receivers on board the vehicles. It is assumed that the angle measurements are corrupted by white Gaussian noise, the variance of which is distance-dependent. Using tools from estimation theory, the problem is converted into that of minimizing, by proper choice of the sensor positions, the trace of the inverse of the Fisher Information Matrix (also called the Cramer-Rao Bound matrix) to determine the sensor configuration that yields the minimum possible covariance of any unbiased target estimator. It is shown that the optimal configuration of the sensors depends explicitly on the intensity of the measurement noise, the constraints imposed on the sensor configuration, the target depth and the probabilistic distribution that defines the prior uncertainty in the target position. Simulation examples illustrate the key results derived.

In this paper acoustic transmitters that were developed for use in underwater neutrino telescopes are presented. Firstly, an acoustic transceiver has been developed as part of the acoustic positioning system of neutrino telescopes. These infrastructures are not completely rigid and require a positioning system in order to monitor the position of the optical sensors which move due to sea currents. To guarantee a reliable and versatile system, the transceiver has the requirements of reduced cost, low power consumption, high pressure withstanding (up to 500 bars), high intensity for emission, low intrinsic noise, arbitrary signals for emission and the capacity of acquiring and processing received signals. Secondly, a compact acoustic transmitter array has been developed for the calibration of acoustic neutrino detection systems. The array is able to mimic the signature of ultra-high-energy neutrino interaction in emission directivity and signal shape. The technique of parametric acoustic sources has been used to achieve the proposed aim. The developed compact array has practical features such as easy manageability and operation. The prototype designs and the results of different tests are described. The techniques applied for these two acoustic systems are so powerful and versatile that may be of interest in other marine applications using acoustic transmitters.

This work has addressed the improving of the multi-path error in positioning systems by coupling a differential global positioning system (DGPS) and double electric compass (DEC) in the navigation system of an orchard robotic vehicle. A novel corrective algorithm model was applied to predicting the positioning coordinates during vehicle movement. The model manipulates a combination of data from both the DEC and the DGPS when the DGPS receiver is in problematic conditions in which the horizontal dilution of precision (HDOP) is higher than three and the number of satellites is fewer than six. The constructed corrective algorithm model, the DEC and the DGPS together form a combined DGPS-DEC system that is inexpensive and of high-precision fitting for a vehicle-guiding instrument. In a field test in an outdoor environment with sections of tree shade in the guiding path, the combined DGPS-DEC positioning system effectively improved the reliability of positioning by correcting the DGPS multi-path error precisely to within 20 cm. By applying a mini-sprayer, further agricultural applications were feasible. In summary, the combined DGPS-DEC positioning system can obtain the correct position of a vehicle in real time for agricultural applications.

Context: Many heuristics-based indoor positioning approaches have been developed to enhance positioning estimation. However, there is no comprehensive survey of these heuristics information and methods.Objective: The main objective of this study is to provide a holistic view and an in-depth analysis of what heuristics information and methods have been used, their general achievements and limitations. This study aims to provide a comprehensive summary to facilitate further research on indoor positioning heuristics.Method: We conducted a systematic literature review (SLR) on indoor positioning heuristics.Results: Ninety-three (93) primary studies were selected. We found two general types of heuristics information and four primary heuristics methods, which we summarised in this paper. We also found that many of these positioning heuristics are tested in experimental settings only. Some heuristics claim practical applications but are not tested for the challenging and typical indoor environments.Conclusion: Most existing heuristics information and methods rely on the assumptions that may not be true in real life environment, hence limiting the usefulness of the positioning outcomes. Based on the analysis of this SLR, we propose two research directions to enhance positioning estimation. [ABSTRACT FROM PUBLISHER]

This paper presents a characterization of an underwater positioning system based on surface nodes equipped with GPS and acoustic transducers. The positioning system calculates the coordinates of an underwater vehicle in one of the surface nodes or beacons, by the emission, detection, and reply of acoustic encoded signals. The characterization of the system has been performed by means of a statistical study, considering different numbers of beacons, beacons’ position and physical phenomena, such as noise, multipath, and Doppler spread. The error propagation caused by these phenomena and the geometrical configuration of the system has been quantitatively assessed in different positioning algorithms, based on trilateration and iterative procedures. The results show how the different phenomena affect the vehicle estimated position errors for the different positioning algorithms. In addition, the obtained errors inside the projected area of the beacons are $\sim 1$ m or lower, rising to a few meters for the worst case scenario, showing the feasibility of the acoustic positioning system. [ABSTRACT FROM AUTHOR]

To replicate classical celestial navigation algorithms with modern technologies, a hemispherical camera array is used to capture panoramic images of the sun for the purpose of obtaining azimuth and zenith angles. A novel geolocation algorithm is presented to use these angles to determine the absolute location without aid of satellites. It derives both the geolocation estimates and the error intervals based on measurement noise levels. Hough Transform, charge-coupled device blooming, and interval analysis are employed to improve accuracy even with lower quality sensors. The proofs of our theoretical results based on an interval analysis handle arbitrary celestial references. Calibration of and geolocation from our experimental prototype demonstrates the feasibility and potential of our system. We obtain geolocation to within a rectangular area of 0.533 km $\times 1.6$ km using an array of inexpensive cameras with 640\times 480$ pixels resolution. Our simulation result shows that the improvement of sensor precision with technology already available can reduce the area of uncertainty to less than 200~{\mathrm{ m}}^{2} . [ABSTRACT FROM PUBLISHER]

This paper describes the genesis, the principle of operation and characteristics of selected radio-navigation positioning systems, which in addition to terrestrial methods formed a system of navigational marking constituting the primary method for determining the location in the sea areas of Poland in the years 1948–2000, and sometimes even later. The major ones are: maritime circular radiobeacons (RC), Decca-Navigator System (DNS) and Differential GPS (DGPS), as well as solutions forgotten today: AD-2 and SYLEDIS. In this paper, due to its limited volume, the authors have omitted the description of the solutions used by the Polish Navy (RYM, BRAS, JEMIOŁUSZKA, TSIKADA) and the global or continental systems (TRANSIT, GPS, GLONASS, OMEGA, EGNOS, LORAN, CONSOL) - described widely in world literature. [ABSTRACT FROM AUTHOR]

This paper presents two acoustic-based techniques for Autonomous Underwater Vehicle (AUV) navigation within an underwater network of fixed sensors. The proposed algorithms exploit the positioning measurements provided by an Ultra-Short Base Line (USBL) transducer on-board the vehicle to aid the navigation task. In the considered framework the acoustic measurements are embedded in the communication network scheme, causing time-varying delays in ranging with the fixed nodes. The results presented are obtained with post-processing elaborations of the raw experimental data collected during the CommsNet13 campaign, organized and scientifically led by the NATO Science and Technology Organization Centre for Maritime Research and Experimentation (CMRE). The experiment involved several research institutions and included among its objectives the evaluation of on-board acoustic USBL systems for navigation and localization of AUVs. The ISME groups of the Universities of Florence and Pisa jointly participated to the experiment with one Typhoon class vehicle. This is a 300 m depth rated AUV with acoustic communication capabilities originally developed by the two groups for archaeological search in the framework of the THESAURUS project. The CommsNet13 Typhoon, equipped with an acoustic modem/USBL head, navigated within the fixed nodes acoustic network deployed by CMRE. This allows the comparison between inertial navigation, acoustic self-localization and ground truth represented by GPS signals (when the vehicle was at the surface). [ABSTRACT FROM AUTHOR]

A recent space weather headline has cast doubt in the minds of some as to whether space weather is the source of spacecraft anomalies, and thus, whether it is important in the design and operation of critical situational awareness, communications, and positioning systems. In this paper, we reiterate the evidence for the importance of space weather, its role in producing spacecraft and ground anomalies, and the threat it poses to critical systems. In addition, we report new studies broken down by anomaly types and suggest the sources of the anomalies (surface charging or interior charging). Finally, we suggest spacecraft charging and ground effects mitigation strategies for design and operations of systems critical to our modern civilization. [ABSTRACT FROM PUBLISHER]