Civil Navigation Research Articles

The 2024 GPS accuracy improvement initiative

Following several performance enhancements, GPS has provided a stable signal-in-space range error (SISRE) of about 50 cm (RMS) for more than a decade. As of early 2024, a major SISRE reduction by about 30% could be noted that helps to maintain the competitiveness of GPS in comparison with the Chinese BeiDou system and reduces the performance difference with respect to the European Galileo system. Based on analyses of onboard clock stability and broadcast navigation messages, the SISRE enhancement can be attributed to a combination of clock switches on selected satellites as well as an overall reduction of the mean time between navigation data uploads. The additional adoption of new transmit antenna phase center offsets in the control segment has no immediate performance impact but affects the comparison of broadcast and precise orbits. Following the aforementioned operational changes, SISRE values for dual-frequency P(Y)-code positioning with the legacy navigation message (LNAV) were found to decrease to roughly 30 cm from March 2024 onward, and marginally worse results are obtained for users of the civil L1/L2 signals and the L2 civil navigation (CNAV) message. Single-frequency LNAV users, on the other hand, experience only a minor benefit, since orbit and clock information improvements are largely masked by the non-availability of group delay information for the L1 C/A signal relative to the L1 P(Y) signal.

TrustCNAV: Certificateless aggregate authentication of civil navigation messages in GNSS

The Global Navigation Satellite System (GNSS) is capable of accurate positioning because it can provide high-precision data. These data are transmitted to the receiver in the form of navigation messages, called civil navigation messages (CNAV). As it is transmitted in an open, transparent environment without data integrity protection mechanisms and secure data transmission measures, the CNAV is suspected to spoofing attacks. In 2023, the OPSGROUP has received approximately 50 reports of GPS spoofing activity. A spoofed plane's navigation system will show it as being in a different place - a security risk if a jet is guided to fly into a hostile country's airspace. To prevent the forging of GNSS positioning data by spoofing attacks targeting CNAV, we propose a certificateless aggregation authentication for CNAV by using the elliptic curve discrete logarithm problem and the combination of the GNAV structural characteristics, called TrustCNAV. Security proof and performance analysis indicate that this authentication scheme can resist spoofing attacks and ensure data security of CNAV, also it avoids pairing operations with high computational complexity, thus meeting security requirements without causing too much time and communication consumption.

Activity of Public Organizations Aimed at Ensuring Health Protection of Women Seafarers

Introduction. Navigation is one of the oldest professions associated with a wide range of factors that negatively affect physical, mental, and social well-being. Besides the general characteristics of the seafarer's profession, the wellbeing of women onboard depends on physiological characteristics, the social environment and the team’s social climate. In international practice, there is a vast experience of the participation of the non-profit sector in addressing issues of seafarers' health. A special attention is paid to women's public organizations, whose activities are focused on women seafarers. The purpose of the study was to review the activities of public (non-governmental, non-profit) women's organizations aimed at protecting the health of civilian female seafarers. Materials and methods. In this research, general scientific research methods were used: analysis, synthesis, generalization, as well as secondary data analysis of the international study “Women Seafarers' Health and Welfare Survey,” where health problems and accessibility of medical care for civilian female seafarers were discussed. Results. Civil navigation, both on land and at sea, is regarded as one of the most difficult professions in the world. Working conditions may lead to a wide range of problems with physical, mental, and emotional well-being of seafarers. Women employed in civil navigation face specific problems related to their health and its protection, as well as to the availability of health care. When the protection of women's health is not supported by the shipowner or ship management team, it can be provided by public organizations of women seafarers.

Assessment of the possible impact on the safety of civil navigation of existing concepts of «navigation pressure»

The features of the global satellite GNSS GPS, as originally a system for military purposes, are considered. The experience of its combat use in recent military conflicts, including during a special military operation, is summarized. Numerous failures in the reception of GPS signals by civilian users, including air carriers and navigators, have been identified when operating GPS in a military environment. The main provisions of the concept of navigation warfare adopted in the United States, one of the elements of which is GNSS GPS and the main goals that it pursues, are considered. An assessment was made of the possible impact of the provisions of the navigational war on the safety of civil navigation and the main directions of work to minimize this impact were outlined. The increasing role and place of nautical astronomy is indicated, as a completely autonomous means of navigation, suitable for use in any area of the World Ocean.

Blockchain-Based Authentication of GNSS Civil Navigation Message

The Civil Navigation Message (CNAV) of the Global Navigation Satellite System (GNSS) is transmitted in an open channel without authentication and integrity protection mechanism. Therefore, the CNAV is facing the threat of interception and tampering, and it is vulnerable to spoofing attacks. To guarantee the authenticity and integrity of CNAV, we propose a cryptographic anti-spoofing scheme of CNAV in GNSS based on consortium blockchain using domestic cryptographic algorithms. In this scheme, we design a CNAV authentication model based on satellites, ground stations and key management center. And implement the authentication protocol to achieve the purpose of preventing CNAV in GNSS from being tampered with. On the basis of the authentication of the entities, the scheme further realizes the functions of information source authentication and integrity protection of the legitimate senders. And on the basis of satisfying security, the protocol has lower computing and communication cost, simplifies the process of re-authentication of information source, and has great practicability for receivers that use civil navigation message to achieve navigation and positioning functions.

Assessing Potential Performance of GPS and Galileo in context of Broadcast Precise Orbits and Clock Corrections

The global navigation satellite system (GNSS) is becoming a vital positioning technology across various services. The ephemeris quality is one of the factors that directly impact the user's position accuracy. Some applications, such as investigations into Earth's crustal dynamics, need more precise ephemeris data than broadcast ephemeris. Several institutions, such as the international GNSS service (IGS), have developed precise orbital services to enable these applications. Unfortunately, data rates for such precise orbits are often confined to 15 minutes. In this paper, in order to generate precise ephemeris with the broadcast sampling period, the well-known Lagrange interpolation method is used. Furthermore, a comparative GPS and Galileo position analysis corresponding to the broadcast and precise ephemeris over a typical day in September 2021 is presented. To get insight into comparative positioning analysis over Hyderabad Station, the ENU (East-North-Up) directional errors, satellite visibility and horizontal accuracy parameters are considered. Based on the numerical analysis, standalone Galileo has similar capabilities to GPS, and it can be used in Multi-GNSS over India and its surrounding areas. This work may help in the development of single- or dual-frequency GNSS receivers for civilian navigation services.

Realistic stochastic modeling considering the PDOP and its application in real-time GNSS point positioning under challenging environments

When the Global Navigation Satellite System (GNSS) is used for positioning under challenging environments, including the natural occlusions and man-made buildings, the signals are easily reflected, diffracted, and even blocked. A stochastic model that conforms to reality is the prerequisite for obtaining high-precision and high-reliability positioning results. However, existing stochastic models which use indicators such as elevation angle and carrier-to-noise ratio cannot reflect the actual situation of the station very well sometimes. Therefore, in this study, in addition to the accuracy of observations, we also consider the impact of the spatial distribution of satellites on positioning accuracy, i.e., position dilution of precision (PDOP). By combining with traditional weighting schemes, the PDOP is considered stochastic modeling. Specifically, different from the previous studies that use PDOP to determine the variance factors between different systems, a new approach is proposed to quantify the contribution of each satellite to PDOP so that the observation weight of each satellite in the system can be appropriately adjusted. The new approach highlights the satellites that contribute much to PDOP and increases the weight of these satellites. Both real static and kinematic data have been tested. The results show that the proposed method is helpful under challenging environments such as high occlusion environments. In civil navigation, the accuracy and reliability of code positioning are improved.

Attacks Against Civilian Objects: An Analysis Under International Humanitarian Law

Civilian airports in recent internal armed conflict are being affected by the military operations of state armed forces and non-state armed groups. A review of the recent internal armed conflict in the middle east shows increase attacks on airports, which often disrupts, altogether halts civilian navigation, and increase the risk of being affected despite the fact that international humanitarian law (IHL) does prohibit such civilian objects attack that violates humanitarian law except in certain situations when it became military objectives. Moreover, military use of airport, may not justify any attack and remains prohibited by other IHL principles. Despite the negative use of civilian airports by the military as a justification to legalize attacking airports, IHL framework restricts this practice. States did not enact national prohibitions or restrictions of military use or limit attacks against civilian airports. However, recent armed conflict indicates that states can counter violation of the protections provided to civilian objects while military use by prohibiting military use of civilian airport. This article argues that states should enact and implement the exceptional rules to attack civilian buildings and forbid military use of civilian airports.

Performance assessment of GNSS-based real-time navigation for the Sentinel-6 spacecraft

The feasibility of precise real-time orbit determination of low earth orbit satellites using onboard GNSS observations is assessed using six months of flight data from the Sentinel-6A mission. Based on offline processing of dual-constellation pseudorange and carrier phase measurements as well as broadcast ephemerides in a sequential filter with a reduced dynamic force model, navigation solutions with a representative position error of 10 cm (3D RMS) are achieved. The overall performance is largely enabled by the superior quality of the Galileo broadcast ephemerides, which exhibits a two- to three-times smaller signal-in-space-range error than GPS and allows for geodetic-grade GNSS real-time orbit determination without a need for external correction services. Compared to GPS-only processing, a roughly two-times better navigation accuracy is achieved in a Galileo-only or mixed GPS/Galileo processing. On the other hand, GPS tracking offers a useful complement and additional robustness in view of a still incomplete Galileo constellation. Furthermore, it provides improved autonomy of the navigation process through the availability of earth orientation parameters in the new civil navigation message of the L2C signal. Overall, GNSS-based onboard orbit determination can now reach a similar performance as the DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) navigation system. It lends itself as a viable alternative for future remote sensing missions.

The Application of Satellite Navigation System in Deformation Monitoring

Global satellite navigation system has become one of the top technical means in the world. The use of satellite navigation in many fields, such as deformation measurement, civil navigation, search resources, geodetic survey, auxiliary precision engineering monitoring and so on, can play its high precision positioning, all-weather monitoring and other technical characteristics. At the same time, satellite navigation system is combined with modern information technology. Internet technology and so on, which realizes the automatic collection, transmission, processing and analysis of safety monitoring data, and the application efficiency is maximized. The present situation and application of satellite navigation system to monitor the deformation of high-rise buildings are studied in this paper. Nowadays, more and more high-rise buildings in the world have sprung up like bamboo shoots. Therefore, how to realize the satellite navigation system to carry on the all-weather, the high precision, the high efficiency monitoring to the high-rise building, carries on the diagnosis to the dangerous signal in time, timely carries on the forecast to the future possible danger and the timely stop loss, this has the very important realistic significance. By reading the literature, the paper expounds the concepts of satellite navigation system, satellite navigation system and Internet technology in detail. The paper mainly takes the high-rise building scaffold as the object of deformation monitoring, and expounds the advantages and reliability of GPS as high-tech for deformation monitoring of high-rise buildings. Finally, through experimental design, the recognition of GPS technology by comparative method reflects the inestimable position of satellite navigation technology.

BD-D1Sec: Protocol of security authentication for BeiDou D1 civil navigation message based on certificateless signature

The BeiDou navigation satellite system (BDS) lacks a security authentication mechanism for BeiDou civil navigation message (BD-CNAV), which faces the threat of information spoofing attacks that may cause errors in positioning and timing information. This paper focuses on the security authentication of BeiDou D1 civil navigation message (BD-D1-CNAV) in BD-CNAV, trying to design a security authentication protocol from the perspective of information authentication. Hence, a protocol of security authentication for BD-D1-CNAV based on certificateless signature is proposed, called as BD-D1Sec protocol. For the purpose of anti-spoofing attacks on BD-D1-CNAV, BD-D1Sec protocol inserts a certificateless signature into the transmission process of BD-D1-CNAV to guarantee the integrity and authenticity of BD-D1-CNAV information without requiring certificate management, which will not reduce the availability of BD-D1-CNAV information. The simulation results show that BD-D1Sec protocol has good authentication and timeliness, a strong ability to resist spoofing attack against BD-D1-CNAV, and has the advantages of low computational complexity and communication cost.

A low-cost IMU/GPS position accuracy experimental study using extended kalman filter data fusion in real environments

In a three-dimensional environment, the navigation of a vehicle in airspace, terrestrial space, or maritime space presents complex aspects concerning the determination of its position, its orientation, and the stability of the processing of the asynchronous data coming from the various sensors during navigation. In this context, this paper presents an experimental analysis of the position accuracy estimated by a low-cost inertial measurement unit coupled, by the extended Kalman data fusion algorithm, with a system of absolute measurements of a positioning system received from a GPS which designates the global positioning system. The different scenarios of the experimental study carried out during this work concerned three tests in a real environment, such as the navigation in a course inside the city of Rabat/Morocco with a moderate speed, a section on the highway at a speed of 120 Km/h and a circular path around a roundabout. The experimental results proved that the low-cost sensors studied are a good candidate for civil navigation applications.

Effects of a navigation spoofing signal on a receiver loop and a UAV spoofing approach

A civil navigation signal is vulnerable to interference and tampering owing to its open interface and low signal power. We focus on navigation spoofing. First, using a piecewise function, we quantitatively analyze the effects of the navigation spoofing signal on the receiver tracking loop. For a phase-locked loop, the spoofing signal extends the pull-in range of the discriminator. The autocorrelation gain of the spoofing signal has a different effect on the slope of the discriminator, depending on whether the discriminator is related to the signal amplitude. For the delay-locked loop, taking the non-coherent early minus late power method as an example, the unlocking condition and interval are analyzed quantitatively using the spoofing amplitude gain and the initial phase cosine of the spoofing and authentic carriers. A carrier frequency difference between the spoofing signal and authentic signal causes a phase jump and attenuation of the amplitude gain. Second, in luring an unmanned aerial vehicle (UAV) to a designated location, we assume a UAV model and provide a spoofing strategy. Experimental results show that it is feasible to lure a civilian quadrotor UAV to a designated location about 50 m from where the UAV believes it is located.

Navigation Message Authentication Based on One-Way Hash Chain to Mitigate Spoofing Attacks for GPS L1

Global Navigation Satellite Systems (GNSS) is vulnerable to significant threats such as spoofing attacks. Data and signal authentication can be used as an effective approach to mitigate such security threats. This paper proposes a Navigation Message Authentication (NMA) method based on Timed Efficient Stream Loss-tolerant Authentication (TESLA), which is using one-way encryption chains. The contributions of this paper are two techniques for implementing TESLA using reserved bits for GPS L1 data. The TESLA algorithm is applied to the extracted navigation message of the GPS L1C/A. Due to the flexibility of the GPS L1C message structure, the protocol is also implemented on Civil Navigation signals (CNAV-2) of GPS L1C. In comparison with Elliptic Curve Digital Signature Algorithm (ECDSA), the Authentication Rate (AR) increases to two minutes for each authentication and performance in term of the Authentication Error Rate (AER) is optimized, by using the TESLA method.

НЕЙРОСЕТЕВОЙ АЛГОРИТМ ПОЛНОКАДРОВОГО РАСПОЗНАВАНИЯ НАДВОДНЫХ ОБЪЕКТОВ В РЕАЛЬНОМ ВРЕМЕНИ

The article explores modern neural network architectures for the automatic detection and recognition of marine surface objects and obstacles of given classes throughout the full image area, applicable for execution in real or near real time on an optoelectronic vision system to au-tomate and improve the safety of civil marine navigation. A formal statement of the problem of automatic detection of objects on images is given. The state-of-the-art algorithms for detecting objects in images based on use of artificial convolutional neural networks were reviewed, their comparison was made and a reasonable choice was made in favor of the most efficient neuralnetwork architecture in terms of computational complexity to recognition accuracy. The subject area is studied, as well as publicly available databases of surface objects suitable for use in the training of algorithms using artificial neural networks. The article concluded that there is insuffi-cient labeled data for training neural network algorithms, as a result of which the authors inde-pendently collected research images and video sequences, prepared and labeled the collected data containing surface marine objects and other obstacles that represent a navigation hazard for ships. Based on the selected neural network architecture, a new neural network algorithm for automatic full-frame detection and recognition of surface objects was developed, and an artificial neural network was trained using the prepared database of images of typical objects. The resulting algorithm was tested by the authors on a validation data set, the quality of its work was estimated using various metrics, and the algorithm’s performance was measured. Conclusions are made about the necessity to expand the collected database of images of typical marine objects, further steps are proposed to improve the accuracy of the developed software and algorithmic complex and its implementation to be used in a marine optoelectronic machine vision system for automa-tion and improving the safety of civil navigation.

GPS System Based Low Cost Maritime Boundary Identification Device

The aim is to build a friendly environment for the Indian fishermen preventing them from facing many hardships. This can be done using GPS(Global Positioning System) that provides navigation, positioning and other time details in all the weather conditions for everyone and everywhere.GPS system being used for map-making, commerce, surveillance. But this paper helps in preventing the violence created between India-Sri Lanka caused for crossing the border IMBL(Indian Maritime Boundary Line) which is unintentional. The important purpose of this paper is to alert the fishermen before crossing the country’s border. If they travelled beyond the border an alert message will be transmitted or sent to the base station by using an X-bee transmitter. This system is developed to help the lives of the fishermen and not to move beyond Indian Boundaries. On the whole it is a plan of creating a suitable device for civilian navigation at low cost.

Frequency tracking out-of-lock control in a resonator fiber-optic gyro.

A resonator fiber-optic gyro (RFOG) is being pursued because of its theoretical potential to meet navigation-grade performance with small size, high precision, and lower cost. The stability of the RFOG operation is based on the synchronization of laser frequency to the fiber ring resonator (FRR) resonance frequency. Frequency tracking out-of-lock will lead to peak pulse and zero-bias change at the output of the RFOG, which seriously degrades the performance. First, the influence mechanism of frequency tracking out-of-lock is analyzed. The change of current and temperature in frequency tracking and the symmetry change caused by backscatter and polarization are the main reasons for the peak pulse and zero-bias error. Second, a scheme of out-of-lock control of the RFOG based on temperature closed-loop operation using digital signal processing is proposed. The improved scheme, signal processing, and implementation method are investigated in detail. Finally, a RFOG prototype is assembled and tested, and 10 min tracking of the laser frequency to the FRR's single-resonance frequency is realized by temperature closed-loop operation. The static performance of the RFOG over 1 h shows that the RFOG output errors caused by frequency tracking out-of-lock are successfully eliminated. The output peak pulse is reduced from 3000 to 200 deg/h, the zero bias is eliminated from 50 to 600 deg/h to 0, and the bias stability of the RFOG is improved from 15.2 to 1.85 deg/h, which indicates a remarkable advance in the performance of the RFOG to satisfy civil navigation application requirements.

Preliminary Analysis of Standalone Galileo and NavIC in the context of Positioning Performance for Low Latitude Region

Abstract The Global and Regional Navigation Satellite Systems (GRNSS) with positioning, navigation and timing (PNT) services are widely used in various navigation applications. Accurate position estimation is the key parameter for any GRNSS. Currently, NavIC is in operational and Galileo is under development. In this paper, the comparative analysis of various parameters of standalone Galileo and the standalone IRNSS (Indian Regional Navigation Satellite System) /NavIC (Navigation with Indian Constellation) satellite configurations are investigated. These parameters are horizontal accuracy parameters, DOP’s (Dilution of Precision) measurements and satellite visibility. To evaluate the performance of Galileo and NavIC, two successive days 13th and 14th August 2018 are considered. The data is acquired from two static mode GNSS receivers located at AGRL (Advanced GNSS Research Laboratory), University College of Engineering, Osmania University, Hyderabad, INDIA (17°24’28.07N, 78°31’4.26E). The results show that Galileo and NavIC systems have significantly shown better performance in terms of considered parameters over the observed periods. This work will be helpful in the integration of NavIC with Galileo for better position accuracy for civilian navigation applications.

BD-II NMA&SSI: An Scheme of Anti-Spoofing and Open BeiDou II D2 Navigation Message Authentication

Due to openness and lack of authentication, like other members of the Global Navigation Satellite System (GNSS) Club, BeiDou-II civilian navigation signals are vulnerable to all kinds of spoofing attacks. As a result, both the positioning and timing functions of BeiDou-II civil satellite navigation are likely to be controlled by the spoofer. In this paper, an anti-spoofing scheme of BeiDou-II Navigation Message Authentication & Spread Spectrum Information (BD-II NMA&SSI) is proposed by using SM cryptographic algorithms and spread spectrum information to resist spoofing attacks. The SM cryptographic algorithms are used for generating authentication information to detect spoofing attacks. The spread spectrum information is to protect the authentication information in the D2 navigation messages from modification. Experimental results show that the scheme guarantees the authenticity of BD-II satellite navigation messages, meets the requirement of anti-spoofing and takes a rather less effect on the satellite navigation system.

Analysis of Various Parameters of L5 and S1 NavIC Signals over Low Latitude Region

Abstract The NavIC/IRNSS (Navigation with Indian Constellation/ Indian Regional Navigation Satellite System) is an autonomous Indian based regional navigation system. The system is intended to provide navigation signals over the Indian region and 1500 kms around. It is necessary to evaluate the performance of NavIC system over the Indian region. In this paper various parameters (Tropospheric delay, C/No, Doppler frequency and vertical ionospheric delay) of the NavIC L5 and S1 signals are evaluated. The analysis is carried out for quiet (26th May, 2017) and disturbed days (28th May, 2017) over low latitude Hyderabad station (17.390 N, 78.310 E), India. The vertical ionospheric delay is the most considerable parameter of NavIC system. In this work, vertical ionospheric delay is estimated using single frequency global ionospheric models like Klobuchar and Grid models. The obtained results are compared with real time NavIC data for both L5 and S1 signals and the results are encouraging. The position accuracy parameters are also evaluated for L5 and S1 modes of receiver operation on a typical day (25th January, 2019). This work finds applications in development of single frequency NavIC receiver for civilian navigation applications.