317,335 research outputs found
MANSEE data analysis results
Results of the data reduction and analysis for the Marine Navigation Systems Evaluation Experiment (MANSEE) are presented. Topics discussed include: the MANSEE test; the navigation sensors which were exercised; the ground truth instrumentation and the processing of ground truth data; and the residual statistics for individual navigation sensors. Residuals were calculated by differencing the actual measurements with anticipated measurements computed from the ground truth trajectory. The results obtained by using the SEAMAP program to filter data from the navigation sensors are also presented. The resultant filtered trajectories were differenced with the corresponding ground truth trajectories to obtain navigation position and velocity errors
Applications of different design methodologies in navigation systems and development at JPL
The NASA/JPL deep space navigation system consists of a complex array of measurement systems, data processing systems, and support facilities, with components located both on the ground and on-board interplanetary spacecraft. From its beginings nearly 30 years ago, this system has steadily evolved and grown to meet the demands for ever-increasing navigation accuracy placed on it by a succession of unmanned planetary missions. Principal characteristics of this system are its capabilities and great complexity. Three examples in the design and development of interplanetary space navigation systems are examined in order to make a brief assessment of the usefulness of three basic design theories, known as normative, rational, and heuristic. Evaluation of the examples indicates that a heuristic approach, coupled with rational-based mathematical and computational analysis methods, is used most often in problems such as orbit determination strategy development and mission navigation system design, while normative methods have seen only limited use is such applications as the development of large software systems and in the design of certain operational navigation subsystems
Distributed data fusion algorithms for inertial network systems
New approaches to the development of data fusion algorithms for inertial network
systems are described. The aim of this development is to increase the accuracy
of estimates of inertial state vectors in all the network nodes, including the
navigation states, and also to improve the fault tolerance of inertial network
systems. An analysis of distributed inertial sensing models is presented and new
distributed data fusion algorithms are developed for inertial network systems.
The distributed data fusion algorithm comprises two steps: inertial measurement
fusion and state fusion. The inertial measurement fusion allows each node to
assimilate all the inertial measurements from an inertial network system, which
can improve the performance of inertial sensor failure detection and isolation
algorithms by providing more information. The state fusion further increases the
accuracy and enhances the integrity of the local inertial states and navigation
state estimates. The simulation results show that the two-step fusion procedure
overcomes the disadvantages of traditional inertial sensor alignment procedures.
The slave inertial nodes can be accurately aligned to the master node
Navigation and attitude reference for autonomous satellite launch and orbital operations
The navigation and attitude reference performance of a strapdown system are investigated for applications to autonomous satellite launch and orbital operations. It is assumed that satellite payloads are integrated into existing missile systems and that the boost, orbit insertion, and in-orbit operation of the satellite are performed autonomously without relying on external support facilities. Autonomous and long term accurate navigation and attitude reference are provided by a strapdown inertial navigation system aided by a star sensor and earth landmark sensor. Sensor measurement geometry and navigation and attitude update mechanizations are discussed. Performance analysis data are presented for following functional elements: (1) prelaunch alignment; (2) boost navigation and attitude reference; (3) post boost stellar attitude and navigation updates; (4) orbital navigation update using sensor landmark measurements; and (5) in-orbit stellar attitude update and gyro calibration. The system performances are shown to satisfy the requirements of a large class of satellite payload applications
Impact of Spoofing of Navigation Systems on Maritime Situational Awareness
The development of contemporary navigation and positioning systems have significantly improved reliability and speeds in maritime navigation. At the same time, the vulnerabilities of these systems to cyber threats represent a remarkable issue to the safety of navigation. Therefore, the maritime community has raised the question of cybersecurity of navigation systems in recent years. This paper aims to analyse the vulnerabilities of the Global Navigation Satellite System (GNSS), Electronic Chart Display Information System (ECDIS) and Automatic Identification System (AIS). The concepts of these systems were developed at a time when cybersecurity issues have not been among the top priorities. Open broadcasts, the absence of or limited existence of data encryption and authentication can be considered as their primary security weaknesses. Therefore, these systems are vulnerable to cyber-attacks. The GPS as the data source of a shipâs position can relatively easily be jammed and/or spoofed, increasing the vulnerabilities of ECDIS and AIS. A systematic literature review was conducted for this article, supplemented by a SWOT analysis of the AIS service and particular case studies of recent cyber-attacks on these systems. The analysis of selected case studies confirmed that these systems could easily be spoofed and become a subject of data manipulation with significant consequences for the safety of navigation. The paper provides conclusions and recommendations highlighting the necessity for the users to be aware of the vulnerabilities of modern navigation systems
Hydrographic Products/Services as a Fundamental Component of the e-Navigation Concept of Operation
e-Navigation is a recent initiative aimed at moving traditional maritime navigation towards a connected digital environment. Defined by the International Maritime Organization (IMO) as âthe harmonized collection, integration, exchange, presentation and analysis of maritime information onboard and ashore by electronic means to enhance birth-to-birth navigation and related services, for safety and security at sea and protection of the marine environmentâ, e-Navigation is not a new system of equipment but more an operational concept. Three significant outcomes are envisioned: 1) Shipboard navigation systems will benefit from the integration of own ship sensors, supporting information, standard user interface, and a comprehensive system for managing guard zones and alerts. Core elements include high-integrity electronic positioning, use of ENCs, and an analysis capability to reduce human error. 2) The management of vessel traffic and related services from ashore will be enhanced through better provision, coordination, and exchange of comprehensive data in formats that will be more easily understood and utilized. 3) A communications infrastructure designed to enable authorised seamless information transfer onboard ship, between ships, between ship and shore and between shore authorities. This paper discusses the main hydrographic-related components, implications for further standards development, some challenges/opportunities, and the role that IHO and others in the hydrographic community should play to facilitate the development and implementation of eNavigation
Robot Navigation in Unseen Spaces using an Abstract Map
Human navigation in built environments depends on symbolic spatial
information which has unrealised potential to enhance robot navigation
capabilities. Information sources such as labels, signs, maps, planners, spoken
directions, and navigational gestures communicate a wealth of spatial
information to the navigators of built environments; a wealth of information
that robots typically ignore. We present a robot navigation system that uses
the same symbolic spatial information employed by humans to purposefully
navigate in unseen built environments with a level of performance comparable to
humans. The navigation system uses a novel data structure called the abstract
map to imagine malleable spatial models for unseen spaces from spatial symbols.
Sensorimotor perceptions from a robot are then employed to provide purposeful
navigation to symbolic goal locations in the unseen environment. We show how a
dynamic system can be used to create malleable spatial models for the abstract
map, and provide an open source implementation to encourage future work in the
area of symbolic navigation. Symbolic navigation performance of humans and a
robot is evaluated in a real-world built environment. The paper concludes with
a qualitative analysis of human navigation strategies, providing further
insights into how the symbolic navigation capabilities of robots in unseen
built environments can be improved in the future.Comment: 15 pages, published in IEEE Transactions on Cognitive and
Developmental Systems (http://doi.org/10.1109/TCDS.2020.2993855), see
https://btalb.github.io/abstract_map/ for access to softwar
GPS Multipath Detection in the Frequency Domain
Multipath is among the major sources of errors in precise positioning using
GPS and continues to be extensively studied. Two Fast Fourier Transform
(FFT)-based detectors are presented in this paper as GPS multipath detection
techniques. The detectors are formulated as binary hypothesis tests under the
assumption that the multipath exists for a sufficient time frame that allows
its detection based on the quadrature arm of the coherent Early-minus-Late
discriminator (Q EmL) for a scalar tracking loop (STL) or on the quadrature (Q
EmL) and/or in-phase arm (I EmL) for a vector tracking loop (VTL), using an
observation window of N samples. Performance analysis of the suggested
detectors is done on multipath signal data acquired from the multipath
environment simulator developed by the German Aerospace Centre (DLR) as well as
on multipath data from real GPS signals. Application of the detection tests to
correlator outputs of scalar and vector tracking loops shows that they may be
used to exclude multipath contaminated satellites from the navigation solution.
These detection techniques can be extended to other Global Navigation Satellite
Systems (GNSS) such as GLONASS, Galileo and Beidou.Comment: 2016 European Navigation Conference (ENC 2016), May 2016, Helsinki,
Finland. Proceedings of the 2016 European Navigation Conference (ENC 2016
Exploring a Geographical Dataset with GEOLIS
International audienceGeographical data are mainly structured in layers of information. However, this model of organisation is not convenient for navigation inside a dataset, and so limits geographical data exploration to querying. We think information retrieval could be made easier in GIS by the introduction of a navigation based on geographical object properties. For this purpose, we propose a prototype, GEOLIS1, which tightly combines querying and navigation in the search process of geographical data. GEOLIS relies on Logical Information Systems (LIS), which are based on Formal Concept Analysis (FCA) and logics. In this paper, we detail data organisation and navigation process in GEOLIS. We also present the results of an experimentation led on a real dataset
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