Viavi 87339, Руководство по эксплуатации

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Global Navigation
Satellite System (GNSS)
This is an umbrella term used to describe a generic satellite-based
navigation/positioning system. It was coined by international agencies such as the
International Civil Aviation Organization (ICAO) to refer to both GPS and GLONASS, as
well as any augmentations to these systems, and to any future civilian developed
satellite system. For example, the Europeans refer to GNSS-1 as being the combination
of GPS and GLONASS, but GNSS-2 is the blueprint for an entirely new system
Global Orbiting
Navigation Satellite
System (GLONASS)
This is the Russian counterpart to GPS. It consists of a constellation of
24 satellites (though the number may vary due to difficulties in funding
for the system) transmitting on a variety of frequencies in the ranges
from 1597-1617MHz and 1240-1260MHz (each satellite transmits on two
different L1 and L2 frequencies). GLONASS provides worldwide
coverage, however, its accuracy performance is optimized for northern
latitudes, where it is better than GPS's SPS (there being no "Selective
Availability" on GLONASS satellites). GLONASS positions are referred
to a different Datum to those of GPS, i.e. PZ90 rather than WGS84.
Global Positioning
System (GPS)
A system for providing precise location which is based on data
transmitted from a constellation of 24 satellites. It comprises three
segments: (a) the Control Segment, (b) the Space Segment, and (c) the
User Segment.
GPS Time (GPST) GPST is a form of Atomic Time, as is, for example, Coordinated
Universal Time (UTC). GPST is "steered" over the long run to keep
within one microsecond of UTC. The major difference is that while "leap
seconds" are inserted into the UTC time scale every 18 months or so to
keep UTC approximately synchronized with the earth's rotational period
(with respect to the sun), GPST has no leap seconds. At the integer
second level, GPST matched UTC in 1980, but because of the leap
seconds inserted since then, GPST is now (end 1998) ahead of UTC by
12 seconds (plus a fraction of a microsecond that varies from day to
day). The relationship between GPST and UTC is transmitted within the
Navigation Message.
Height (Orthometric) The Orthometric Height is the height of a station on the earth's surface,
measured along the local plumbline direction through that station, above
the Geoid surface. It is approximated by the "Height Above Mean Sea
Level", where the MSL Datum is assumed to be defined by the mean tide
gauge observations over several years. The relationship between
Orthometric Height (H) and Ellipsoidal Height (h) is : h = H + N, where N
is the Geoid Height or Geoid Undulation with respect to the Reference
Ellipsoid. Orthometric Height is traditionally derived from geodetic
leveling (using such techniques as optical leveling, trigonometrical
leveling, barometric leveling.
Inter-Channel Bias The difference in the code (or carrier) phases between two
simultaneously simulated signals from the same satellite on different
frequencies, excluding any effects from the propagation path or
deliberately introduced errors, and after applying any corrections that
are broadcast in the navigation message.
Inter-Frequency Bias The difference in the code (or carrier) phases between two
simultaneously simulated signals from the same satellite on different
frequencies, excluding any effects from the propagation path or
deliberately introduced errors, and after applying any corrections that
are broadcast in the navigation message.
Inter-Sub-carrier Bias The difference in the code (or carrier) phases between any two
sub-carriers (e.g. I and Q) of the same signal.
Term Description