TRANSNAV The International Journal on Marine Navigation and Safety of Sea Transportation, 2016
The understanding of the ionospheric effects on GNSS positioning performance forms an essential p... more 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.
Location-based service (LBS) development is firmly based on the reliable and accurate position re... more Location-based service (LBS) development is firmly based on the reliable and accurate position reporting system. In addition to rover-based positioning performance requirements, the position reporting system has to provide secure means of transferring position-related data between rover and location server. Here we describe the realisation of the position reporting system, based on GPS, HTTPS and GPRS technologies. Our approach allows secure position-related data transfer, with solution simplicity maintained. The automatic position reporting system (APRS) architecture is in compliance with current trends in telecommunications, promising successful integration with emerging mobile communications technologies.
Space weather is a common name for the group of physical and chemical processes taking place in t... more Space weather is a common name for the group of physical and chemical processes taking place in the vast space between the Sun and the Earth. Caused primarily by the solar activity, those processes create a flow of materia and energy. When directed to the Earth and its surroundings, this flow disrupts magnetic and ionospheric conditions, affecting numerous technical systems
ABSTRACT With increasing attractiveness of location-based services (LBS), the need for consistent... more ABSTRACT With increasing attractiveness of location-based services (LBS), the need for consistent establishment and deployment of the LBS Quality of Service (QoS) hierarchy is strongly demanded. The position estimation is in the heart of every location-based service. Thus, LBS QoS is primarily concerned with position estimation performance, including position estimation errors and response time, achieved by either single position sensor, or a combination of several position estimation sensors and methods. Common LBS QoS establishment approach consists of either “as-is” (i. e. no-guarantee) or “best-effort” (again no-guarantee, but with some concern) approach. The proposed new solution starts with generic description of LBS QoS and methods for its deployment. As the result a method emerges that utilises position estimation by adaptive selection of positioning sensors based on requested QoS.
Automatic identification system (AIS) is among the most important advanced maritime navigation sy... more Automatic identification system (AIS) is among the most important advanced maritime navigation systems introduced recently. It is aimed to provide increased safety on the seas through dedicated reporting scheme for navigation data exchange between the vessels and coastal monitoring stations. After recognizing the shortcomings of present VHF AIS solution, our team proposed transition of AIS functionalities to mobile Internet, offering
Ionospheric disturbances are the proven cause of degradation of the GNSS performance. Resulting f... more Ionospheric disturbances are the proven cause of degradation of the GNSS performance. Resulting from the space weather processes, ionospheric disturbances modify the vertical ionospheric profile, thus changing the Total Electron Content (TEC) encountered by satellites' rays on their way towards the GNSS receiver. Here we report a case of the shortlived ionospheric disturbance, detected by SID monitor located at the GNSS laboratory, Faculty of Maritime Studies in Rijeka, Croatia, and the effects it causes to the GPS positioning performance, as observed by the singlefrequency maritime GPS receiver situated at the same venue. Observed correlation between GPS and SID monitor observables points to perspective of establishing a model for the ionospheric disturbances identification, which is to be examined further in the mid-term research.
2013 21st Telecommunications Forum Telfor (TELFOR), 2013
Success of Location-Based Services (LBS), a subset of mobile communication services, suffers from... more Success of Location-Based Services (LBS), a subset of mobile communication services, suffers from the lack of multidisciplinary co-operation due to misunderstandings caused by deployment of unilateral development models. Here we propose the re-definition of the essential terms and processes, that results in creation of the new LBS operational model, thus allowing for the enhanced and more fruitful multidisciplinary collaboration on LBS development.
ABSTRACT Although standard satellite positioning provides unbeatable performance, compared with o... more ABSTRACT Although standard satellite positioning provides unbeatable performance, compared with other available positioning methods it still suffers from many environment-related issues. One of them is disruption of continuity of positioning service, usually caused by temporal inability to collect navigation data due to poor satellite visibility. This problem is particularly noticeable in urban areas, where high buildings often considerably decrease the satellite visibility. A number of GPS-based systems and services (among them the location-based services - LBS) rely upon continuous provision of satellite positioning service. In order to decrease as much as possible the time to first fix (TTFF) after temporal unavailability of standard positioning service, auxiliary communications systems deploy the functionality of assistance data provision to satellite positioning receiver. This article examines the content of satellite positioning assistance, the impact of assistance data on position estimate calculation algorithm and the means for assistance data distribution. Special emphasis is given on satellite positioning assistance for LBS, and the mechanisms for assistance data delivery through the mobile communication network are presented. In conclusion, assistance data are identified as the major contributor to satellite positioning performance improvement, with a brief list of related future activities given
Ionospheric errors are the most influential source of the GPS positioning errors. In an attempt t... more Ionospheric errors are the most influential source of the GPS positioning errors. In an attempt to at least partially improve the GPS positioning process, a global ionospheric correction model is introduced within the standard GPS positioning service. Referred to as the Klobuchar model after its inventor, this model appeared as a compromise between computation complexity and correction accuracy. Unfortunately, the Klobuchar model is capable of correcting up to 70% of ionospheric errors, with particularly poor performance during severe ionospheric disturbances. Wide implementations of satellite navigation systems (GPS in particular) in modern technical systems call for better corrections of the ionospheric influence. This article presents three essential approaches in modelling the GPS ionospheric errors (physical, empirical and dynamic models) and discusses their implementation in GPS-based technical systems
Ionospheric delay is the major source of satellite positioning system performance degradation. De... more Ionospheric delay is the major source of satellite positioning system performance degradation. Designers of satellite positioning systems attempt to mitigate the impact of the ionospheric delay by deployment of correction models. For instance, the American GPS utilises a global standard (Klobuchar) model, based on the assumption that the daily distribution of GPS ionospheric delay values follows a biased cosine curve during day-time, while during the night-time the GPS ionospheric delay remains constant. Providing a compromise between computational complexity and accuracy, the Klobuchar model is capable of correcting up to 70% of actual ionospheric delay, mainly during quiet space weather conditions. Unfortunately, it provides a very poor performance during severe space weather, geomagnetic and ionospheric disturbances. In addition, a global approach in Klobuchar model development did not take into account particularities of the local ionospheric conditions that can significantly contribute to the general GPS ionospheric delay. Current research activities worldwide are concentrating on a better understanding of the observed GPS ionospheric delay dynamics and the relation to local ionosphere conditions.
ABSTRACT Recent studies confirm the importance of satellite positioning in location-based service... more ABSTRACT Recent studies confirm the importance of satellite positioning in location-based services (LBS) development. A field study was conducted in suburban and rural areas near Zagreb, Croatia in order to examine the real-time data compliance with recently established positioning performance requirements for LBS quality of service (QoS). Data analysis was based on comparison between actual positioning performance and pre-specified positioning parameter values using defined comparative procedures. The results presented here confirm a good correlation between the actual and required positioning performance, even without implementation of any of augmentation or assistance positioning methods.
Location-based services (LBS) have already found their place in modern world of telecommunication... more Location-based services (LBS) have already found their place in modern world of telecommunications and their future is certainly not questionable. However, LBS quality of service (QoS) definition is still in its infancy, preventing fast and concerting LBS development.
TRANSNAV The International Journal on Marine Navigation and Safety of Sea Transportation, 2016
The understanding of the ionospheric effects on GNSS positioning performance forms an essential p... more 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.
Location-based service (LBS) development is firmly based on the reliable and accurate position re... more Location-based service (LBS) development is firmly based on the reliable and accurate position reporting system. In addition to rover-based positioning performance requirements, the position reporting system has to provide secure means of transferring position-related data between rover and location server. Here we describe the realisation of the position reporting system, based on GPS, HTTPS and GPRS technologies. Our approach allows secure position-related data transfer, with solution simplicity maintained. The automatic position reporting system (APRS) architecture is in compliance with current trends in telecommunications, promising successful integration with emerging mobile communications technologies.
Space weather is a common name for the group of physical and chemical processes taking place in t... more Space weather is a common name for the group of physical and chemical processes taking place in the vast space between the Sun and the Earth. Caused primarily by the solar activity, those processes create a flow of materia and energy. When directed to the Earth and its surroundings, this flow disrupts magnetic and ionospheric conditions, affecting numerous technical systems
ABSTRACT With increasing attractiveness of location-based services (LBS), the need for consistent... more ABSTRACT With increasing attractiveness of location-based services (LBS), the need for consistent establishment and deployment of the LBS Quality of Service (QoS) hierarchy is strongly demanded. The position estimation is in the heart of every location-based service. Thus, LBS QoS is primarily concerned with position estimation performance, including position estimation errors and response time, achieved by either single position sensor, or a combination of several position estimation sensors and methods. Common LBS QoS establishment approach consists of either “as-is” (i. e. no-guarantee) or “best-effort” (again no-guarantee, but with some concern) approach. The proposed new solution starts with generic description of LBS QoS and methods for its deployment. As the result a method emerges that utilises position estimation by adaptive selection of positioning sensors based on requested QoS.
Automatic identification system (AIS) is among the most important advanced maritime navigation sy... more Automatic identification system (AIS) is among the most important advanced maritime navigation systems introduced recently. It is aimed to provide increased safety on the seas through dedicated reporting scheme for navigation data exchange between the vessels and coastal monitoring stations. After recognizing the shortcomings of present VHF AIS solution, our team proposed transition of AIS functionalities to mobile Internet, offering
Ionospheric disturbances are the proven cause of degradation of the GNSS performance. Resulting f... more Ionospheric disturbances are the proven cause of degradation of the GNSS performance. Resulting from the space weather processes, ionospheric disturbances modify the vertical ionospheric profile, thus changing the Total Electron Content (TEC) encountered by satellites' rays on their way towards the GNSS receiver. Here we report a case of the shortlived ionospheric disturbance, detected by SID monitor located at the GNSS laboratory, Faculty of Maritime Studies in Rijeka, Croatia, and the effects it causes to the GPS positioning performance, as observed by the singlefrequency maritime GPS receiver situated at the same venue. Observed correlation between GPS and SID monitor observables points to perspective of establishing a model for the ionospheric disturbances identification, which is to be examined further in the mid-term research.
2013 21st Telecommunications Forum Telfor (TELFOR), 2013
Success of Location-Based Services (LBS), a subset of mobile communication services, suffers from... more Success of Location-Based Services (LBS), a subset of mobile communication services, suffers from the lack of multidisciplinary co-operation due to misunderstandings caused by deployment of unilateral development models. Here we propose the re-definition of the essential terms and processes, that results in creation of the new LBS operational model, thus allowing for the enhanced and more fruitful multidisciplinary collaboration on LBS development.
ABSTRACT Although standard satellite positioning provides unbeatable performance, compared with o... more ABSTRACT Although standard satellite positioning provides unbeatable performance, compared with other available positioning methods it still suffers from many environment-related issues. One of them is disruption of continuity of positioning service, usually caused by temporal inability to collect navigation data due to poor satellite visibility. This problem is particularly noticeable in urban areas, where high buildings often considerably decrease the satellite visibility. A number of GPS-based systems and services (among them the location-based services - LBS) rely upon continuous provision of satellite positioning service. In order to decrease as much as possible the time to first fix (TTFF) after temporal unavailability of standard positioning service, auxiliary communications systems deploy the functionality of assistance data provision to satellite positioning receiver. This article examines the content of satellite positioning assistance, the impact of assistance data on position estimate calculation algorithm and the means for assistance data distribution. Special emphasis is given on satellite positioning assistance for LBS, and the mechanisms for assistance data delivery through the mobile communication network are presented. In conclusion, assistance data are identified as the major contributor to satellite positioning performance improvement, with a brief list of related future activities given
Ionospheric errors are the most influential source of the GPS positioning errors. In an attempt t... more Ionospheric errors are the most influential source of the GPS positioning errors. In an attempt to at least partially improve the GPS positioning process, a global ionospheric correction model is introduced within the standard GPS positioning service. Referred to as the Klobuchar model after its inventor, this model appeared as a compromise between computation complexity and correction accuracy. Unfortunately, the Klobuchar model is capable of correcting up to 70% of ionospheric errors, with particularly poor performance during severe ionospheric disturbances. Wide implementations of satellite navigation systems (GPS in particular) in modern technical systems call for better corrections of the ionospheric influence. This article presents three essential approaches in modelling the GPS ionospheric errors (physical, empirical and dynamic models) and discusses their implementation in GPS-based technical systems
Ionospheric delay is the major source of satellite positioning system performance degradation. De... more Ionospheric delay is the major source of satellite positioning system performance degradation. Designers of satellite positioning systems attempt to mitigate the impact of the ionospheric delay by deployment of correction models. For instance, the American GPS utilises a global standard (Klobuchar) model, based on the assumption that the daily distribution of GPS ionospheric delay values follows a biased cosine curve during day-time, while during the night-time the GPS ionospheric delay remains constant. Providing a compromise between computational complexity and accuracy, the Klobuchar model is capable of correcting up to 70% of actual ionospheric delay, mainly during quiet space weather conditions. Unfortunately, it provides a very poor performance during severe space weather, geomagnetic and ionospheric disturbances. In addition, a global approach in Klobuchar model development did not take into account particularities of the local ionospheric conditions that can significantly contribute to the general GPS ionospheric delay. Current research activities worldwide are concentrating on a better understanding of the observed GPS ionospheric delay dynamics and the relation to local ionosphere conditions.
ABSTRACT Recent studies confirm the importance of satellite positioning in location-based service... more ABSTRACT Recent studies confirm the importance of satellite positioning in location-based services (LBS) development. A field study was conducted in suburban and rural areas near Zagreb, Croatia in order to examine the real-time data compliance with recently established positioning performance requirements for LBS quality of service (QoS). Data analysis was based on comparison between actual positioning performance and pre-specified positioning parameter values using defined comparative procedures. The results presented here confirm a good correlation between the actual and required positioning performance, even without implementation of any of augmentation or assistance positioning methods.
Location-based services (LBS) have already found their place in modern world of telecommunication... more Location-based services (LBS) have already found their place in modern world of telecommunications and their future is certainly not questionable. However, LBS quality of service (QoS) definition is still in its infancy, preventing fast and concerting LBS development.
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Papers by R. Filjar
degradations for various modes of GNSS SDR receiver operation, and identified the benefits of utilisation of multi‐GNSS and ionospheric error correction techniques.
degradations for various modes of GNSS SDR receiver operation, and identified the benefits of utilisation of multi‐GNSS and ionospheric error correction techniques.