![]() It shows the time and the detailed orbital information of the broadcasting satellite. Ephemeris An ephemeris is one of the information that each GNSS satellite broadcasts. This identification can be easily done by checking either the GNSS system ID in the GSA sentences or the talker ID of GSV sentences. However, users of GNSS receivers sometimes have to determine to which constellation the PRN1 belongs to. Duplicate PRN Since the PRN numbers are defined by satellite constellations, it is common for the GPS satellite PRN1 and the Galileo satellite PRN1 to be present at the same time. GNSS receivers receive these PRN codes, as the key of each satellite, to determine from which satellite the message came. For example, the GPS L1C/A signal uses 32 PRN sequences to uniquely identify each of its 32 operational satellites, which are referred to as PRN1 to PRN32. Each PRN sequence of a satellite constellation is referred to by a serial number, also called PRN number. (Pseudo Random Noise) PRN stands for Pseudo random noise and refers to the PRN sequence or gold code, a unique and periodical pattern broadcasted by each operational navigation satellite. SVN are used by the entities managing the satellite constellations, while users of GNSS receivers use PRN numbers to identify navigation satellites. Some of these SVNs are operational and others are decommissioned due to the satellite having reached its lifespan. For example, for the GPS satellites, as of November 2020, SVN from 1 to 77 have been issued. It is the serial number given to each navigation satellite and each satellite constellation is assigned a non-overlapping numbers. (Space Vehicle Number) SVN stands for Space Vehicle Number. There is a possibility that some of the broadcast contents may be changed accordingly. An ICD is not a permanent specification definition, but may be revised to correct errors or to enhance functionality. Each satellite constellation has its own ICDs, and GNSS receivers are generally designed with reference to these documents. The ICDS of a GNSS are published by the relevant department of the country that operates this satellite constellation. ICDs are formal documents that specify the interface between the signals of a satellite constellation and the receiver. ICD ICD stands for Interface Control Document. But in the GNSS industry, each satellite system managed by a different country or coalition of countries is referred to as a satellite constellation, like GPS of USA, GLONASS of Russia, Galileo of Europe Union and BeiDou of China. Satellite constellation A constellation is a group of stars. Navigation Satellite System covering a more limited area, such as QZSS and NavIc, are classified as Regional Satellite Navigation Systems (RNSS). GPS, Galileo, GLONASS and BDS/BeiDou are Global Navigation Satellite Systems. GNSS Global Navigation Satellite System (GNSS) is a general term describing any satellite constellation that provides Positioning, Navigation and Timing (PNT) information data on a global basis. Geostationary satellite systems like MSAS (Japan), WAAS (USA), EGNOS (EU), GAGAN (India) and some others are SBAS. The differential correction information can be used for positioning to improve the position accuracy. These augmentation messages provide integrity functions, differential correction information, and ranging functions. SBAS Satellite-Based Augmentation System (SBAS) is a regional geostationary satellite system that broadcasts, on the same L1 frequency as GPS, GNSS augmentation messages to improve the precision of the position and time of GNSS receivers. QZSS, also known as MICHIBIKI, covers Japan, East Asia and Oceania, with 4 satellites on a elliptical geosynchronous orbit, maximizing their availability at high elevation over Japan. QZSS Quasi-Zenith Satellite System (QZSS) is a RNSS owned by the government of Japan and operated by QZSS Services Inc (QSS). NavIc covers a large area centered around the South of the Indian Subcontinent with 7 satellites as of 2020. NavIC was previously called Indian Regional Navigation Satellite System (IRNSS). NavIC Navigation Indian Constellation (NavIC) is a RNSS owned and operated by the Government of India. Beidou BeiDou Navigation Satellite System (BDS) is a GNSS owned and operated by the People's Republic of China. Galileo Galileo is a GNSS owned by the European Union and operated by the European GNSS Agency (GSA). ![]() GLONASS is also known as "URAGAN" which means storm in Russian. GLONASS Global Navigation Satellite System (GLONASS) is a GNSS owned and operated by the Russian Federation. GPS's standard positioning service started in 1993. Terms related to satellite systems and satellite signals GPS Global Positioning System (GPS), whose full name is NAVSTAR GPS, is the oldest GNSS and owned by the United States government and operated by the United States Space Force.
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