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Determining the user’s position using Global Navigation Satellite System (GNSS) data depends on the presence of errors in the satellite part of the system, random errors, errors in the system environment, and user errors. If we systematically neglect and do not apply the error reduction algorithms and process the available input position records of the observed GNSS satellites identically, the differences in position accuracy can be attributed to the effect of the geometric position of the satellite expressed by the GDOP (Geometric Dilution Of Precision) coefficient. At the same time, the number of visible satellites is observed considering the applied elevation mask. The results indicate that the differences in the geometric positioning of the satellites and the orbits lead to a non-uniform accuracy of the user’s position, which depends on the latitude of the user’s position. The key parameter is the elevation mask, whereby increasing the number of visible satellites does not contribute to increased accuracy

In the proposed paper, the research study of smartphones' satellite positioning performance has been described. The research consisted of static (at fixed position) and dynamic (during sea navigation) segment. It was conducted in confined coastal area of middle Dalmatia (bay of Zaton). Using several mobile devices as handheld GNSS receivers (smartphones with GPS and both GPS & GLONASS satellite navigation systems' applications), positioning patterns were measured and recorded. In subsequent statistical analysis, positions derived from DGPS device were used as references. The results of data analysis confirmed improvements in satellite positioning by means of multi-constellation usage. Employing and integrating various GNSS systems, positioning error can be measurably reduced, together with increased integrity of the positioning service.

Short introduction User equivalent ranging error (UERE) GPS ionospheric delay Multipath effects GPS/GNSS error budget Geometric dilution of precision Algorithm for positioning point determination Total GPS positioning determination error Corrections regarding multipath, ionospheric delay... Advanced systems (augmentation and assistance) Differential GPS Satellite based augmentation systems EGNOS Satellite signal multi-frequency processing GNSS

Satellite navigation has taken inevitable place over everyday life. It has become a part of the infrastructure of the most of the world countries. In early phases of its development, satellite positioning was limited to military purposes. Later it was expanded to merchant naval and air navigation. Nowadays, satellite positioning application is global. GNSS receivers can be found in almost every road vehicle, not to mention GPS applications in today's cell phones. With the development of satellite systems, it has become evident that the environment of the Earth represents an essential element in determination of position via satellites. Moreover, among all satellite positioning error components, it is the signal propagation medium (Earth's atmosphere) that dominates with its influence on the position accuracy. In the proposed paper, a short overview of global GNSS services is given, defining all current operational systems and principles of determining the position. The establishment and operation of the GNSS Navigational Laboratory is presented, with special emphasis on research on Earth's charged atmosphere – ionosphere, as a main factor for position accuracy degradation.

Dear colleagues, dear friends, This year I had the honour of writing you a few introductory words. First of all, I cannot tell you enough how happy I am to see you live again, or rather offline. It has not been easy to get through this strange time. We have been dealing with a global pandemic caused by the coronavirus, which has really disrupted a lot of things, including many conferences and meetings around the world. Unfortunately, some of them have either closed down altogether or the organisers have decided to go online only. Apart from the fact that the development of technology nowadays does not allow us to communicate easily through various applications, which we all had the pleasure to get to know, we are still convinced that nothing can replace direct contact, discussions, making contacts, establishing new ones and/or deepening existing ones, all in the most classical way – live and on site. Given the above reasons and constraints, we also struggled with various hybrid approaches during the pandemic, but at no point did we think of postponing the conference. Just as it was not easy for others, it was not easy for us either, but that is why we are even happier and prouder to welcome you this year at the 16th Baška GNSS Conference and the 3rd Workshop on Smart, Blue and Green Maritime Technologies in a row. If we look back a few years, the Baška conference was traditionally primarily focused on GNSS and related technologies and applications. In the meantime, we have expanded it with the Workshop on Smart, Blue and Green Maritime Technologies, with which we actually wanted not only to attract a larger number of interested researchers, but also to additionally emphasise the connection between satellite navigation systems and all other maritime fields, especially in the context of guidance, navigation and control of modern vessels. Nowadays, we can truly say that we are witnessing an incredibly rapid development of technologies based primarily on artificial intelligence, but also on other advanced computational solutions, which in turn is directly reflected in the possibilities of autonomous systems and autonomous vessels in general. The synergy of satellite navigation technologies, inertial navigation, classical and intelligent sensors, ship hydrodynamics, energy systems and propulsion, digitalisation, automation, robotics, artificial intelligence, security, etc. has never been more in the spotlight than in recent times, and will continue to be so in the coming period. In this context, we want to ensure that our conference remains a lever for holding constructive discussions in the aforementioned areas in the future. None of this would have been possible without the synergy of all of us, i.e. everyone who contributed in some way – keynote speakers, authors and coauthors of papers, presenters of papers and posters, reviewers, members of the International Programme Committee and the Organising Committee. A heartfelt thank you to them all. A big thank you also goes to our institutions, i.e. the coorganisers of the event, for their active support and help, both in terms of organisation and logistics as well as in financially. I believe that the difficult times are now slowly behind us and that we will meet and socialize in even greater numbers at the next conference, to which I cordially and openly invite you. Be well and take care.

Global Navigation Satellite Systems (GNSS) have found their place as the primary positioning method in maritime navigation. In terms of new technologies that can further enhance conventional GNSS capabilities, Real-Time Kinematics (RTK) is the most promising technology for advanced maritime requirements. To obtain and use such data, GNSS must be integrated with equipment using Inertial Navigation Systems (INS), implementing advanced estimation algorithms and filters. Such an implementation enables the aided system performance. This study presents an analysis of one such possible integration conducted in the Bay of Kvarner, Croatia. During the measurement campaign, the reference station Rijeka from the CROPOS network was used as the RTK base station. The main aim of the work was to compare the ideal ship heading without draught with the real one under different conditions. The results obtained can be the prerequisites for estimating the process noise caused by the ship dynamics under the influence of environmental loads.

The satellite navigation can no longer be observed on its own. It is represented almost everywhere, with basic and advanced services implemented in all segments of everyday life. The book you have in front of you contains selected papers from the 2021 Baška event, which took place in the period from 10 to 12 May, in Baška on the island of Krk, Croatia. This year’s event had a special connotation for several reasons. After the 2020 corona outbreak and the consequent lockdown, and given that the measures were still globally present, the gathering was held in a hybrid form, using multiple remote communication platforms, combined with in situ attendance. The organisation and realisation of the hybrid event as a whole were challenging, but we believe it was managed smoothly, constructively and to the satisfaction of all participants. In one way or another – shoulder to shoulder, or interacting through screens across the globe. The event comprised two segments. The Annual Baška GNSS Conference, the core event, was held for the fourteenth time, meaning for the fourteenth year in a row. It brought together a range of academic community members, students, professionals and enthusiasts, who presented their research results in the field of satellite navigation, and beyond. The second part was a novelty. For the first time, the Workshop on Smart, Blue and Green Maritime Technologies took place. The vision of the Workshop was (and still is) to enhance current and future navigation applications to a broader research area, with a focus on technologies and solutions for safer, more reliable and greener shipping. The traditional conference concentrated on more application-oriented means and related improvements of existing, as well as the build-up of emerging maritime technologies. During the conference, 22 scientists presented the results of their research. In addition to specialist sections, eight invited lectures were held by world renowned experts and scientists in the field of satellite navigation and new maritime technologies. The event was attended by approximately 70 participants. Virtual discussions were held after each section during both conference and the workshop events. We coined the term ‘virtual coffee break’, which proved to be an excellent way of communication and further networking. The results could already see the light of day in 2022, in the same place, at about the same time. The event was jointly organised by the Royal Institute of Navigation, London, the Faculty of Maritime Studies and Faculty of Engineering of the University of Rijeka, the Faculty of Transport and Traffic Sciences of the University of Zagreb, and the University of Zadar, Maritime Department. The whole event was held under the high auspices of the European Academy of Sciences and Arts, Salzburg, and the Croatian Academy of Engineering, Zagreb. Perhaps it is needless to say, but we are genuinely proud of the successful realisation of the event, especially nowadays, when scientific conferences have become rarer and even ceased owing to well-known reasons. Our decision on organising the event in the first place, and then holding it ‘live’ (at least partially), proved to be justified, right and necessary as well, given that the spirit of the conference was maintained. It seems that we succeeded, both during the Baška days, as well as here, in presenting the research outputs in a published form. Many people should be given credit for this event, starting with organisers, members of our international and local committees, hotels’ (extra kind) personnel, reviewers, but most of all, the contributors. The authors are the true reason why are you reading this, dear reader. And maybe, next time, it could be you. Editors

Ovo je knjiga proširenih sažetaka znanstvenog skupa '15th Baška GNSS Conference and The 2nd Workshop on Smart, Blue and Green Maritime Technologies', Baška, otok Krk, 8. - 13. svibnja 2022. godine.

Cilj ovog rada je prikazati usporedno parcijalnu analizu relativnih odstupanja položaja putem GPS (engl. Global Positioning System) i GLONASS (rus. Globalnaya Navigazionnaya Sputnikovaya Sistema) globalnih navigacijskih satelitskih sustava u polarnim predjelima. Ova tema je važna za uspješno vođenje broda, tj. navigacije broda u sve više prometnijim polarnim predjelima. U radu su obrađeni globalni i regionalni navigacijski sustavi koji se danas koriste i dalje razvijaju, a sve kako bi se povećala brzina i točnost prijenosa signala do korisnika za dobivanje što točnijeg položaja. U pomorskoj navigaciji netočan položaj može biti vrlo opasan, dok u oceanskoj, a posebice navigaciji u polarnim predjelima može značiti dodatno vrijeme plovidbe, dodatni utrošak pogonskog goriva a posebno nesigurnost za brod i posadu. Potreban je sve veći razvoj GNSS sustava na način da se razvijaju SBAS sustavi (engl. Satellite Based Augmentation System), odnosno WAAS (engl. Wide Area Augmentation System) sustav za područje SAD, EGNOS (engl. European Geostationary Navigation Overlay Service) sustava za područje Europe i ostali sustavi koji danas osiguravaju pokrivenost gotovo cijele zemaljske kugle kvalitetnim satelitskim signalom. Pristup ocjenjivanju pogrešaka položaja zadanih stanica učinjen je statističkom analizom skupa podataka koji sadrži zapise položaja izmjerenih na izabranim stanicama u odabranom vremenskom razdoblju. Statističkoj analizi prethodio je izbor uzorka nad kojim će se vršiti analiza, a zatim priprema podataka koja je bila neophodna. Da bi se mogla uspješno napraviti statistička obrada podataka trebalo je izabrati i kvalitetan uzorak. Nakon provjere dostupnosti podataka odabran je period ispitivanja od sedam dana i rezultati tog ispitivanja izneseni su u ovom diplomskom radu. U ovome radu može se vidjeti koji čimbenici utječu na nešto lošije određivanje položaja satelitskim sustavima u polarnim predjelima u odnosu na ostale dijelove Zemlje. Isto tako napravljena je usporedba skupa statističkih podataka o zapisanim položajima GPS sustava i GLONASS sustava iz koje vidimo kako je GPS sustav nešto točniji nego GLONASS., The purpose of this paper is to present comparative partial analysis of relative positioning deviations of GPS and GLONASS global navigation satellite systems in polar areas. This subject is of great interest for successful ship management, i.e. ship navigation in polar regions as areas of increased traffic. The paper analyses the positioning performance of global and regional navigation systems that are still in use today and continuously developing, all in order to increase the speed and accuracy of signal transmission to the final user for obtaining the most accurate position. In maritime navigation, an incorrect position can be very dangerous. Moreover, when it comes to oceans and navigation in polar regions, it can mean additional sailing time, additional fuel consumption and especially it could threaten the security of the ship and crew. This is the reason why continuous development of GNSS system is required and this development should follow improvement of SBAS system (Satellite Based Augmentation System), respectively WAAS (Wide Area Augmentation System) system for the area of United States, EGNOS (European Geostationary Navigation Overlay Service) system for European continent and other systems that today provide coverage of almost the entire globe with a quality signal. The approach to estimate the position errors was done by statistical analysis of a data sets containing records of the positioning solutions measured at the selected stations in the selected time period. To make statistical analysis, firstly was required on which the analysis will be preformed, and then the preparation of the data that was necessary. In order to be able to successfully preform statistical data processing, a quality sample had to be selected. After checking data availavility a test period of seven days was selected and the results of that test are presented in thethesis. In this paper it can be seen which factors influence the somewhat worse positioning of satellite systems in the polar regions compared to other parts of the Earth. Moreover, comparison research of a set of statistical data on the recorded positions of the GPS system and the GLONASS system was made from which we can conclude that the GPS system is somewhat more accurate than the GLONASS system.

The paper analyses variability of the ionospheric Total Electron Content (TEC) over European middle latitudes, obtained from Global Navigation Satellite Systems (GNSS) observations. Although characteristics of the ionospheric activity at middle latitudes are usually well modelled compared to low and high latitudes, models usually do not take into account the local irregularities and response very slowly to fast developing ionospheric disturbances. To detect ionospheric irregularities and obtain information of ionospheric gradients, we used the TEC rate of change (ROT) and calibrated vertical TEC (VTEC) data. For observation of spatial behaviour of ionospheric fluctuations we used TEC data from several GNSS stations situated in the same geographical area. A tool for geographical representation of VTEC values and the TEC rate of change (ROT) was developed. Produced graphical and numerical representation was used for preliminary analyses of ionospheric fluctuations over middle latitudes during the periods of low and high geomagnetic activity.

Total Electron Content (TEC), proportional to the ionospheric error in Global Navigation Satellite Systems (GNSS), can be calculated using dual-frequency measurements. To improve the calculation accuracy TEC should be calibrated, i.e. the inter-frequency biases introduced in the satellites and the receiver should be removed. Data from GNSS reference stations is publicly available in Receiver Independent Exchange Format (RINEX). Several software tools can be used to process such files. Modifying pseudoranges and carrier-phase data by removing the calibrated TEC, a version of the original RINEX file that does not contain ionospheric error was made. Modification procedure’s validity was proven by performance evaluation in position domain. Such a modified RINEX file could be used as a reference in comparison of different ionospheric error correction methods in position domain, where the methods would also be represented forming RINEX files modified following the same procedure.

Given the wide scope of possibilities that GNSS may provide in terms of environmental protection, the authors point elaborate in particular the land use land cover (LULC) aspect in monitoring the state of the environment and for drawing up future physical plans that would safeguard the quality of living and that of the environment. Various stakeholders in the communities in vulnerable coastal karst regions or the mountains should be provided easy and non- costly access to detailed LULC data which could be processed and converted to quantifiable indicators of the degree of human intervention in the environment and its possible degradation. The availability of understandable indicators would ensure sound public participation and consultation in deciding on land use.