The Usefulness of GLONASS for Positioning in the Presence of GPS in the Indian Subcontinent

Augmentation of GNSS Utility by IRNSS/ NavIC Constellation Over the Indian Region

Abstract: Indian region is expected to receive signal from multiple satellite-based navigation systems for multi-GNSS hybrid operation. Even in presence of GPS, GLONASS and GALILEO signals together, it is regularly found that, during some parts of the day no GNSS satellite is available above 60° elevation angle from large parts of India. This may cause problem in seamless navigation solutions in the locations, where visibility of the satellites is also obstructed in the lower elevation angles, which is a common feature in Indian urban conditions; the situation also degrades satellite geometry. IRNSS/NavIC is Indian indigenous regional navigation system operational since 2016. This paper presents theoretical, simulated and initial results of real-time studies on IRNSS/NavIC visibility from India using a IRNSS-GPS-SBAS (IGS) receiver. The studies show that, in such situations of inferior GNSS satellite visibility, IRNSS/NavIC operating together with GPS, can augment this time-dependent degraded visibility conditions. The Indian satellite navigation system ensures presence of at least one satellite above 60° elevation for use with GPS over the Indian region, supports multi-GNSS operation towards seamless solution, and improves satellite geometry.

GPS/GNSS Current Bibliography

Abstract: This quick bibliography is a compilation of recently published peer-reviewed articles describing original research with citations that may be of interest to other investigators working in any of the GPS/GNSS fields. Titles of new books and conference proceedings that include a significant number of chapters and/ or articles dealing with GPS/GNSS are also listed in italics in this bibliography. Articles, primarily appearing in trade journals, containing interspersed advertisements are only identified by their first page number followed by the symbol +. Contributions with more than five authors will be referenced under the first author name and the extension et al.

Impact of multiconstellation satellite signal reception on performance of satellite‐based navigation under adverse ionospheric conditions

Abstract: Application of multi-constellation satellites to address the issue of satellite signal outages during periods of equatorial ionospheric scintillations could prove to be an effective tool for maintaining the performance of satellite-based communication and navigation without compromise in accuracy and integrity. A receiver capable of tracking GPS, GLONASS and GALILEO satellites is operational at the Institute of Radio Physics and Electronics, University of Calcutta, Calcutta, India located near the northern crest of the Equatorial Ionization Anomaly (EIA) in the Indian longitude sector. The present paper shows increased availability of satellites combining GPS, GLONASS and GALILEO constellations from Calcutta compared to GPS-only scenario and estimates intense scintillation-free (S4 < 0.6) satellite vehicle look angles at different hours of the post-sunset period 19:00-01:00LT during March 2014. A representative case of March 1, 2014 is highlighted in the paper and overall statistics for March 2014 presented to indicate quantitative advantages in terms of scintillation-free satellite vehicle look angles that may be utilized for planning communication and navigation channel spatial distribution under adverse ionospheric conditions. Number of satellites tracked and receiver position deviations has been found to show a good correspondence with the occurrence of intense scintillations and poor user receiver-satellite link geometry. The ground projection of the 350-km subionospheric points corresponding to multi-constellation shows extended spatial coverage during periods of scintillations (0.2 < S4 < 0.6) compared to GPS.

Studies on solution accuracy of GLONASS from India

Abstract: GLONASS is declared fully operational in its revitalized form since late 2011. This generated interest for using it for redundancy and system independence and for a robust Multi-GNSS navigation environment. This paper discusses the accuracy capabilities of revitalized GLONASS in standalone and in mixed mode of operation with GPS on basis of studies made using real-life data from different parts of India collected over 2012–2014. The results show the potentials of GLONASS as an independent global navigation system and the advantages of it as an active component of usable Multi-GNSS from India and the surrounding regions.

Lifetime Performances of Modernized GLONASS Satellites: A Review

Abstract: Abstract GLONASS, successfully operating during 1990s became unusable by early 2000s. Following a revitalization and modernization plan since 2004, GLONASS constellation has been completed again by the end of 2011 and the use of GLONASS is gaining popularity. Because of the previous experience, some scepticism exists among the stakeholders in using GLONASS for reliable solution and application development. This paper critically reviews the operational lifespan of GLONASS satellites launched between 2004 and 2016, as this is an important contributor towards reliability and sustained operation of the system. For popularization and extracting full benefits of GLONASS as stand-alone system or as an active component of multi-GNSS, major issues of assuring the minimum sufficient GLONASS constellation (of 24…23 satellites), efficient design implementation and the modernized ground control segment development and operation need to be properly taken care of by the system operators.

A study on GPS PDOP and its impact on position error

Abstract: It is well established that 3-dimensional position error in position fix through GPS network should increase with PDOP value provided the range error estimates remain constant. To study this aspect an elaborate experimental observation was carried out for one complete year. These data have been systematically analysed. It has been seen that for maximum percentage of time optimum PDOP values lie between 2 and 4. Study on the variations of 3-dimensional position errors on PDOP reveals that position errors increase proportionately up to the value of· 6. Aftelwards the change of position errors with PDOP is almost random in nature. Possibly beyond this value of PDOP, the position errors are governed by some other factors.