GLONASS User Segment

GLONASS
Title	GLONASS User Segment
Author(s)	GMV
Level	Basic
Year of Publication	2011

The GLONASS User Segment consists on L-band radio receiver/processors and antennas which receive GPS signals, determine pseudoranges (and other observables), and solve the navigation equations in order to obtain their coordinates and provide a very accurate time.

GLONASS Receivers

A GLONASS Receiver is a device capable of determining the user position, velocity and precise time (PVT) by processing the signal broadcasted by satellites.

Any navigation solution provided by a GNSS Receiver is based on the computation of its distance to a set of satellites, by means of extracting the propagation time of the incoming signals traveling through space at the speed of light, according to the satellite and receiver local clocks.

Notice that satellites are always in motion, so previous to obtaining the navigation message, the satellite’s signal is detected and tracked. The receiver’s functional blocks that perform these tasks are the antenna, the front-end and the baseband signal processing (in charge of acquiring and tracking the signal).

Once the signal is acquired and tracked, the receiver application decodes the navigation message and estimates the user position. The Navigation Message includes:

• Ephemeris parameters, needed to compute the satellite’s coordinates
• Time parameters and Clock Corrections, to compute satellite clock offsets and time conversions
• Service Parameters with satellite health information
• Ionospheric parameters model needed for single frequency receivers
• Almanacs, needed for the acquisition of the signal by the receiver. It allows computing the position of all satellites but with a lower accuracy than the ephemeris

The ephemeris and clocks parameters are usually updated every half-an-hour, whereas the almanac is updated at least every six days.

The GLONASS Signal In Space is specified in the following documents:

• IS-GPS-200E: Interface between the space segment of the Global Positioning System and the navigation user segment of the GPS for radio frequency link 1 (L1) and link 2 (L2)

Receivers can be categorized by their type in different ways, and under different criteria. For instance, receivers can be stand-alone, or may benefit from corrections or measurements provided by augmentation system or by receivers in the vicinities (DGPS). Moreover receivers might be generic all purpose receivers or can be built specifically having the application in mind: navigation, accurate positioning or timing, surveying, etc. In addition to position and velocity, GPS receivers also provide time. An important amount of economic activities, such wireless telephone, electrical power grids or financial networks rely on precision timing for synchronization and operational efficiency. GLONASS enables the users to determine the time with a high precision without needing to use expensive atomic clocks.

Applications

GLONASS applications are all those applications that use GLONASS to collect position, velocity and time information to be used by the application. Global navigation and time synchronization service of unlimited number of users on ground, on sea, airborne and in space. Access to civilian signal of the system is provided to Russian and foreign users free of charge and withour any restrictions:

• Armed Forces
• Communication and energy systems synchronization
• Geodesy: GLONASS and GLONASS\GPS receivers are used to determine precise coordinates of points and land parcel boundaries
• Cartography: GLONASS is used in civilian and military cartography
• Tectonics: tectonic plates movements and convulsions are tracked using satellites
• Navigation: global positioning systems are used for maritime and roadway navigation
• Satellite monitoring: ERA-GLONASS project is motor vehicle position and velocity monitoring and control over their movements
• Complex engineering structures monitoring
• Animals monitoring, environmental protection
• Search and rescue facilitation
• Personal trackers, "panic button"

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