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1

Signal research for alternative Baltic Navigation System

Dziewicki M., Młotkowski J., Stupak T.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2020

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Vol. 14. no. 4

799--802

EN

In the project R-Mode a navigation system for Baltic Sea is designed. In the range of these actions in summer of 2020 the signal for DGPS base station Rozewie were adopted and measurements on the sea were performer. This experiment is shown in the article.

2

Reconstruction of geomagnetic event as observed in Northern Adriatic region and Its correlation with GPS single-frequency positioning deviations

Brčić D., Ćelić J., Valčić S.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2020

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Vol. 14, no. 2

349--357

EN

Space weather effects are generally recognized as causes of degradation of satellite positioning, navigation and timing (PNT) services. We analyze GPS position estimation error during a geomagnetic storm, focusing on manifestations of geomagnetic processes. The position estimation error was analyzed in terms of GPS coordinates’ deviations (latitude, longitude and height) from their reference values. The storm’s impact was studied in the Northern Adriatic region where GPS observables from two Global Navigation Satellite System (GNSS) reference stations were analysed. Geomagnetic indices were elaborated, comprising readings from interplanetary, magnetospheric and geomagnetic observatories. Total Electron Content (TEC) on both stations was computed using dual frequency GPS pseudorange observables. The experiment was to reconstruct the movement of geomagnetic disturbances entering the geospace, reaching the earth’s surface. The aim was to correlate possible space weather manifestation on satellite positioning performance in terms of positioning error. Regularities in changes in positioning deviations were identified with relation to influential indices. The research offered a possibility of experimental positioning deviations assessment as well as forecasting. Evaluation of generated rudimentary Classification and Regression Trees (CART) models showed that the risk of satellite positioning errors could be assessed and predicted considering absolutes, as well as changes in values of geomagnetic indices. During the research process, several activities emerged as preferable continuation of the work, with the aim of further development of predictive models and the complement of space weather scenarios and their consequences on navigational systems. Along with summarized results, they are outlined in the conclusion section.

3

Determination of seabed heights in the area of Polish territorial waters in the official reference system

Rogowski J. B., Galas R., Kłęk M.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2020

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Vol. 14, no. 2

339--342

EN

The determination of the height in the vertical reference frame in force in Poland is based both on national regulations (Council of Ministers Regulation, 2012) and on the resolution adopted by the EUREF subcommittee in Tromsø (Resolution No. 5, EUREF Symposium, 2000). Currently, the PL-KRON86-NH vertical reference frame is in use in Poland – a normal height system referred to a quasi-geoid of the average level of the Baltic Sea determined by the zero level of the mareograph in Kronstadt. According to the Regulation, by the end of 2019, Poland will adopt the PL-EVRF2007-NH vertical reference frame, i.e. a normal height system referred to the zero level of the mareograph in Amsterdam. The authors present a method of determining normal heights of seabed referred to the zero level of the mareograph in Amsterdam for coastal areas of the Baltic Sea. This method uses GNSS measurements, the EGM 2008 model and depth measuring methods typical for underwater mining.

4

Analysis of tropospheric contribution to GPS positioning error during tropospheric cyclone Marcus in 2018

Sikirica N., Horvat M., Špoljar D., Rumora I.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2020

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Vol. 14, no. 2

343--348

EN

GNSS positioning performance assessment is essential for sustainable development of a growing number of GNSS-based technology and socio-economic applications. Case-studies of GNSS positioning performance in critical environments and applications scenarios reveals vulnerabilities of the GNSS Positioning, Navigation, and Timing (PNT) services, and suggest mitigation techniques and GNSS application risk containment. Here we address the case of GPS positioning performance during a devastating tropical cyclone Marcus that hit the greater area of the city of Darwin, Australia in 2018. We identified specific statistical properties of time series of tropospheric contribution to GPS northing, easting, and vertical positioning error that may contribute to understanding of tropospheric effects on GPS positioning performance during a massive weather deterioration in maritime and coastal areas, and analysed their adversarial effects on GNSS-based maritime applications.

5

Polish DGPS System: 1995-2018 – studies of reference station operating zones

Specht C., Specht M., Dąbrowski P. S.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2019

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Vol. 13, no. 3

581--586

EN

The operating zone of a radio navigation system is one of its main operating features. It determines the size of a water body in which the system can be used, while guaranteeing vessels’ navigation safety. The DGPS system in the LF/MF range is now the basic positioning system in coastal waters around the world, which guarantees not only metre positioning accuracy, but it is also the only one to provide navigators with signals on positioning reliability. This paper describes and summarises over twenty years of studies dealing with the operating zone of the Polish DGPS reference station network. This paper is the fifth in a series of publications whose aim was to present in detail the process of installation, testing and long-term evaluation of the navigational parameters of the Polish DGPS system, launched in 1995. This paper includes the theoretical foundations of determination of the Dziwnów and Rozewie DGPS reference station operating zones in the years 1995-2018. Moreover, it presents the measurement results for the signal levels and the results of their analyses, which determine the station operating zones.

6

Logistic map-encrypted Chaotic Ranging code as a proposed alternative to GNSS PRN Pseudorange Code

Filić M., Dimc F.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2019

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Vol. 13, no. 3

587--590

EN

Pseudo-Random Noise (PRN) Gold code was selected for utilisation as the Global Navigation Satellite System (GNSS) pseudo-range measurement code sequence. Recent studies revealed a potential security vulnerability issue due to the Gold PRN code utilisation in a GNSS-related cyber-attack known as GNSS spoofing. Here a PRN code construction method based on chaotic-form logistic map is proposed as an alternative to the existing Gold code practice. Dubbed Chaotic Ranging Code (CRC), is a PRN code generation method that generates ranging code with orthogonal properties as good as, if not better, then those of the Gold PRN code, while assuming the encryption embedded in the proposed CRC code provides improved GNSS information security.

7

GNSS positioning error change-point detection in GNSS Positioning Performance Modelling

Filić M., Filjar R.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2019

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Vol. 13, no. 3

575--579

EN

Provision of uninterrupted and robust Positioning, Navigation, and Timing (PNT) services is essential task of Global Navigation Satellite Systems (GNSS) as an enabling technology for numerous technology and socio-economic applications, a cornerstone of the modern civilisation, a public goods, and an essential component of a national infrastructure. GNSS resilience may be accomplished only with complete understanding of the causes of GNSS positioning performance disruptions and degradations, presented in a form of applications- and scenarios-related models. Here the application of change-point detection methods is proposed and demonstrated in a selected scenario of a fast-developing ionospheric storm’s impact on GNSS positioning performance, as a novel contribution to forecasting GNSS positioning performance model development and GNSS utilisation risk mitigation.

8

Errors of UAV autonomous landing system for different radio beacon configurations

Kelner J. M., Ziółkowski C.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2019

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Vol. 13, no. 2

429--435

EN

At the turn of the 20th and 21st centuries, development of microelectronics and microwave techniques allowed for minimization of electronic devices and systems, and the use of microwave frequency bands for modern radio communication systems. On the other hand, the global navigation satellite system (GNSS) have contributed to the popularization of radio navigation in civilian applications. These factors had a direct impact on the development and dissemination of unmanned aerial vehicles (UAVs). In the initial period, the UAVs were used mainly for the army needs. This results also from the legal aspects of the UAV use in the airspace. Currently, commercial UAVs for civilian applications, such as image recognition, monitoring, transport, etc., are presented increasingly. Generally, the GNSS system accuracy for the UAV positioning during a flight is enough. However, the GNSS use for automatic takeoff and landing may be insufficient. The extensive, ground-based navigation support systems used at airports by manned aircraft testify to these. In the UAV case, such systems are not used due to their complexity and price. For this reason, the novel dedicated take-off and landing systems are developed. The proposal of the autonomous landing system, which is based on the Doppler effect, was presented in 2017. In this case, the square-based beacon configuration was analyzed. This paper shows the influence of various beacon configurations in the Doppler-based landing system on the positioning error during the UAV landing approach.

9

Determination of flying objects position

Dzunda M., Dzurovcin P., Melniková L.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2019

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Vol. 13, no. 2

423--428

EN

This paper describes various methods of flying object positioning with the emphasis on their accuracy. Based on the accomplished analysis, we will select the most appropriate method to determine the position of a flying object for relative navigation purposes. The primary criterion for choosing a positioning method is the accuracy of distance measurement within users working in the aviation communications network. The results presented in the paper have been based on mathematical modelling and computer simulation performed in the Matlab programming environment. The results obtained can be used to navigate flying or non-flying objects that work in the air communications network.

10

SBAS/EGNOS enabled devices in maritime

López M., Anton V.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2018

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Vol. 12, no. 1

23--27

EN

Nowadays, it is a fact that Global Navigation Satellite Systems (GNSS) have become the primary means of obtaining Position, Navigation and Timing (PNT) information at sea. Most of the ships in the world are equipped with GNSS receivers. And currently these users take advantage of different augmentation systems such as DGNSS or SBAS/EGNOS, as they provide an adequate answer, especially in terms of accuracy and integrity. To take advantage of this improved accuracy, direct access to EGNOS in vessels can be achieved through EGNOS-enabled navigation receivers and EGNOS-enabled AIS transponders. Therefore, the natural question is: Are those GNSS receivers SBAS (EGNOS) enabled? In most cases they are; SBAS is being used. This paper provides an analysis of the number of onboard devices, mainly devoted to navigation purposes and AIS transponders, which are SBAS compatible.

11

Foundations of GNSS spoofing detection and mitigation with distributed GNSS SDR receiver

Filić M.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2018

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Vol. 12, no. 4

649--656

EN

GNSS spoofing is an intentional and malicious action aimed at degrading and suppressing GNSS Positioning, Navigation, and Timing (PNT) services. Since it affects data and information segment of GNSS, it is considered a GNSS information (cyber‐) security attack. Considering a significant and powerful threat, GNSS spoofing should be treated seriously to avoid damage and liabilities resulting from disruptions of GNSS PNT services. Here the GNSS position estimation procedure is examined for potential vulnerabilities, and the nature of and motivation for GNSS spoofing attacks exloiting the vulnerabilities assessed. A novel GNSS Spoofing Detection and Mitigation (GNSS SDM) method is proposed within the established computational and communication infrastructure, that allows for successful overcoming and classification of GNSS spoofing attacks. Proposed method is applicable without requirements for core GNSS modification, and leaves majority of user equipment easily transferable to the GNSS spoofing‐free environment. Potential GNSS spoofing effects and GNSS anti‐spoofing opportunities in maritime sector were given a particular attention.

12

Availability of the GNSS geodetic networks position during the hydrographic surveys in the ports

Specht C., Makar A., Specht M.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2018

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Vol. 12, no. 4

657--661

EN

Geodetic network GNSS receivers are more commonly associated with positioning systems used in maritime hydrography. In terms of positioning accuracy when no terrain obstacles are present, they meet international hydrographic surveys standards (S‐44) fully. Those standards are defined as 1m (0.95) for Exclusive Order and 2m (0.95) for Special Order. It is equally as important to ensure access to position which error is not higher than above mentioned maximum values. This is most often determined by the density of port infrastructure. This article presents the results of analysis of availability of hydrographic system that operates based on geodetic GNSS networks. Hydrographic surveys in question were undertaken in inner basins with diverse infrastructure. Three representative types of ports were selected for this reason: fishing type (Hel), medium sized, modern commercial type (Gdynia) and highly congested, narrow canal type (Gdansk – Motlawa). A nonpublic, geodetic GNSS network was used for all surveys. It is worth mentioning that the above network is at the moment the only available network that provides both GPS and GLONASS corrections. The surveys provided evidence that geodetic GNSS networks can be successfully utilised to determine position of hydrographic vessel in low and moderately developed ports as well as in Exclusive and Special Orders. In highly congested ports however, the availability of the above mentioned method of measurement can be insufficient to realise a survey.

13

An experimental identification of multipath effect in GPS positioning error

Rumora I., Sikirica N., Filjar R.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2018

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Vol. 12, no. 1

29--32

EN

The analysis of the GPS multipath effects in maritime environment is constrained with the practice of traditional GPS receiver design, that prevents access to GPS signals in Base-band Processing Domain. Here we propose and validate a simple method for experimental identification of multipath effect in Navigation Processing Domain, based on spectral characterisation of time series of GPS positioning errors.

14

A South Pacific Cyclone-caused GPS positioning errorand Its impact on remote oceanic island communities

Filić M., Filjar R.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2018

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Vol. 12, no. 4

663--670

EN

Satellite navigation gains importance in sustainable development of modern civilisation. With the increasing number of GNSS-based technology and socio-economic systems and services, satellite navigation has become an essential component of national infrastructure. This calls for novel requirements on GNSS positioning perfomance, and increasing need for resilient GNSS development. Here we examined the impact of rapidly developing tropical cyclone on GPS positioning performance degradation, and the resulting impact on oceanic non-navigation and navigation GPS applications. We presented the methodology for indirect simulation-based GPS positioning performance evaluation through utilisation of experimental GPS observations, GNSS Software-Defined Radio (SDR) receiver, and a statistical analysis and framework we developed in the R environment for scientific computing. We identified alteration of GPS positioning error components time series statistical properties, and discuss the potential impact on GPS-based services essential for remote oceanic island communities. Manuscript concludes with the summary of findings, proposal for recommendations on improved GNSS resilience, and an outline for future research.

15

Global Navigation Satellite Systems – Perspectives on Development and Threats to System Operation

Czaplewski K., Goward D.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2016

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Vol. 10, no. 2

183--192

EN

The rapid development of satellite navigation and timing technologies and the broad availability of user equipment and applications has dramatically changed the world over the last 20 years. It took 38 years from the launch of the world’s first artificial satellite, Sputnik 1, (October 4, 1957) to the day NAVSTAR GPS became fully operational (July 17, 1995). In the next 20 years user equipment became widely available at the consumer level, and 10 global and regional satellite systems were partially or fully deployed. These highly precise signals provided free to the user have been incorporated by clever engineers into virtually every technology. At the same time interference with these signals (spoofing and jamming) have become a significant day to day problem in many societies and pose a significant threat to critical infrastructure. This paper provides information on the current status and development of navigation satellite systems based on data provided by the systems' administrators. It also provides information on Loran/eLoran, a system which many nations have selected as a complement and backup for satellite navigation systems.

16

Conception of EGNOS Integrity Data Utilization in ENC Systems

Bilewski M., Zalewski P.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2016

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Vol. 10, no. 3

389--393

EN

The paper presents the processing of EGNOS integrity data received either directly from the satellite network or the Sisnet internet relay. Relationship between the individual frames in EGNOS messages has been described. Usefulness of these data was indicated by the three examples. In the first example data form EGNOS was used to compare integrity parameters and the calculated position error. In further examples the simulated position with error and calculated integrity parameters were implemented together. The results were presented in two ways: with use of dedicated program which presents only ship contours (the one not covering GNSS uncertainty and the one covering this uncertainty called Marine Vessel Protection Area) and as a layer in existing ECDIS.

17

BeiDou and Galileo, Two Global Satellite Navigation Systems in Final Phase of the Construction, Visibility and Geometry

Januszewski J.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2016

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Vol. 10, no. 3

381--387

EN

Spatial segment is one of three segments of each satellite navigation systems (SNS). Nowadays two SNSs, GPS and GLONASS, are fully operational, two next SNSs, BeiDou in China and Galileo in Europe, are in final phase of the construction. In the case of China system this segment will consist of 35 satellites with three types of orbits ? medium (MEO), geostationary (GEO) and inclined geosynchronous (IGSO). As GEO and IGSO satellites can be used in China and Asia-Pacific region only, BeiDou MEO constellation with 27 fully operational satellites will be taken into account in this paper. The orbital planes of the Galileo constellation will be divided in “slots” that contains at least one operational satellite. The Galileo reference constellation has 24 nominal orbital positions or operational slots in MEO homogeneously distributed in 3 orbital planes; i.e. 8 slots equally spaced per plane. As the error of user’s position obtained from both systems depends on geometry factor DOP (Dilution Of Precision) among other things the knowledge of the number of satellites visible by the user above given masking elevation angle Hmin and the distributions of DOP coefficient values, GDOP in particular, is very important. The lowest and the greatest number of satellites visible in open area by the observer at different latitudes for different Hmin, the percentage of satellites visible above angle H, distributions (in per cent) of satellites azimuths and GDOP coefficient values for different Hmin for BeiDou and Galileo systems at different latitudes are presented in the paper.

18

An SDR-based Study of Multi-GNSS Positioning Performance During Fast-developing Space Weather Storm

Filić M., Filjar R., Ruotsalainen L.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2016

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Vol. 10, no. 3

395--400

EN

The understanding of the ionospheric effects on GNSS positioning performance forms an essential pre-requisite for resilient GNSS development. Here we present the results of a study of the effects of a fast-developing space weather disturbance on the positioning performance of a commercial-grade GPS+GLONASS receiver. Using experimentally collected pseudoranges and the RTKLIB, an open-source software-defined GNSS radio receiver operating in the simulation mode, we assessed GNSS positioning performance degradations for various modes of GNSS SDR receiver operation, and identified the benefits of utilisation of multi-GNSS and ionospheric error correction techniques.

19

Nominal and Real Accuracy of the GPS Position Indicated by Different Maritime Receivers in Different Modes

Januszewski J.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2014

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Vol. 8, no. 1

11--19

EN

Nowadays on the ship’s bridge two or even more GPS receivers are installed. As in the major cases the coordinates of the position obtained from these receivers differ the following questions can be posed – what is the cause of this divergence, which receiver in the first must be taken into account etc. Based on information published in annual GPS and GNSS receiver survey it was estimated the percentage of GPS receivers designed for marine and/or navigation users. The measurements of GPS position based on the four different stationary GPS receivers were realized in the laboratory of Gdynia Maritime University in Poland in the summer 2012. The coordinates of the position of all these receivers were registered at the same time. The measurements in mode 3D were made for different input data, the same for all receivers. The distances between the individual unit’s antenna were considered also. Next measurements in mode 3D also were realized on two ships in different European ports. Additional measurements were made in mode 2D with three receivers for different their’s antenna heights. The results showed that the GPS position accuracy depends on the type of the receiver and its technical parameters particularly.

20

A Matlab Implementation of Differential GPS for Low-cost GPS Receivers

Ali Q, Montenegro S.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2014

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Vol. 8, no. 3

343--350

EN

A number of public codes exist for GPS positioning and baseline determination in off-line mode. However, no software code exists for DGPS exploiting correction factors at base stations, without relying on double difference information. In order to accomplish it, a methodology is introduced in MATLAB environment for DGPS using C/A pseudoranges on single frequency L1 only to make it feasible for low-cost GPS receivers. Our base station is at accurately surveyed reference point. Pseudoranges and geometric ranges are compared at base station to compute the correction factors. These correction factors are then handed over to rover for all valid satellites observed during an epoch. The rover takes it into account for its own true position determination for corresponding epoch. In order to validate the proposed algorithm, our rover is also placed at a pre-determined location. The proposed code is an appropriate and simple to use tool for post-processing of GPS raw data for accurate position determination of a rover e.g. Unmanned Aerial Vehicle during post-mission analysis.