• Journal of Positioning, Navigation, and Timing
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• v.9 no.3
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• pp.237-248
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• 2020

GNSS has been evolving dramatically in recent years. There are currently 6 GNSS (4 GNSS, AND 2 RNSS) constellations, which are GPS (USA), GLONASS (Russia), BeiDou (China), Galileo (EU), QZSS (Japan), and IRNSS (India). The Number of navigation satellites is expected to be over 150 by 2020. As the number of both constellations and satellites used for the improvement of positioning performance, high accuracy, and robustness of precise positioning is more promising. However, a large amount of the correction messages is required to support the augmentation system for the available satellites of all the constellations. Since bandwidth for the correction messages is generally limited, sending or scheduling the correction messages might be a critical issue in the near future. In this study, we analyze the relationship between the size of the bandwidth and Real-Time Kinematics (RTK) performance. Multiple Signal Messages (MSM), the only Radio Technical Commission for Maritimes (RTCM) message that supports multi-constellation GNSS, has been used for this assessment. Instead of the conventional method that broadcasts all the messages at the same time, we assign the MSM broadcasting interval for each constellation in 5 seconds. An open sky static and dynamic test for this study was conducted on the roof of Sejong University. Our results show that the RTK fixed position accuracy is not affected by the 5-second interval corrections, but the ambiguity fixing rate is degraded for poor DOP cases when RTK correction are transmitted intermittently.

• Journal of Navigation and Port Research
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• v.42 no.1
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• pp.17-24
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• 2018

The Russian Global Navigation Satellite System (GLONASS) has been fully recovered since October 2011, and it has been significantly modernized. The recently launched GLONASS 752 was set for successful performance on October 16, 2017 and has resulted in 24-satellite constellation with 22 second-generation (GLONASS-M) satellites, and a third-generation (GLONASS-K) satellite. Therefore, this paper is focused on not only the identified navigation parameters, but also the performance analysis of the project based on its real data received from the studied satellites. It is verified that the 5-11 satellites are available for receiving navigation signal at this time. The obtained values of GDOP, PDOP, HDOP, VDOP, and TDOP are 2.790, 2.424, 1.169, 2.123, and 1.381, noted respectively in standard deviation. In fact, the level of positioning precision is about 1.4m in standard deviation. As a result, the positioning performances of the measured GLONASS and GPS are virtually identical. Therefore, we determine that the GLONASS is expected to be expanded for future applications.

• Korean Journal of Remote Sensing
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• v.19 no.3
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• pp.181-190
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• 2003

Since the operation of the first satellite-based navigation service, satellite positioning has played an increasing role in both surveying and geodesy, and has become an indispensable tool for precise relative positioning. However, in some situations, e.g. at a low angle of elevation, the use of satellites for navigation is seriously restricted because obstacles like buildings and mountains can block signals. As a mean to resolve this problem, the quasi-zenith satellite system has been proposed as a next-generation satellite navigation system. Quasi-zenith satellite is a system which simultaneously deploys several satellites in a quasi-zenith geostationary orbit so that one of the satellites always stay close to the zenith if viewed from a specific point on the ground of East Asia. Thus, if a position measurement function compatible with CPS is installed in the quasi-zenith and stationary satellites, and these satellites are utilized together with the CPS, four satellites can be accessed simultaneously nearly all day long and a substantial improvement in position measurement, especially in metropolitan areas, can be achieved. The purpose of this paper is to evaluate the effectiveness of quasi-zenith satellite system on positioning accuracy improvement through simulation by using precise orbital information of the satellites and a three-dimensional digital map. Through this developed simulation system, it is possible to calculate the number of simultaneously visible satellites and available area for positioning without the need of actual observation. Furthermore, this system can calculate the Dilution Of Precision (DOP) and the error distribution.