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| ICAO |
International Civil Aviation Organization |
| IMO |
International Maritime Organization |
| Inclination |
The angle between the orbital plane of a body and some reference
plane (e.g. E Equatorial plane). |
| Initialization |
Refers to the simple procedure of telling a new GPS receiver
"where it is", when it is turned on for the first
time. Information required includes: approximate present position
in latitude/longitude coordinates; and the current local time
and date. |
| Inmarsat |
International Maritime Satellite. |
| INS |
Inertial Navigation System, which contains an inertial measurement
unit (IMU). |
| Integer ambiguity (bias term) |
The receiver counts the radio waves from the satellite, as
they pass the antenna, to a high degree of accuracy. However,
it has no information on the number of waves (complete wavelengths)
there were between the satellite and the antenna when it started
counting. This unknown number of wavelengths between the satellite
and the antenna is the integer ambiguity. Resolving the integer
ambiguity for each satellite is an essential part of differential
processing for land surveying applications. |
| Integrated Doppler |
A measurement of Doppler shift frequency or phase over time. |
| Integrity |
The ability of a system to provide timely warnings to user
when the system should not be used for navigation as a result
of errors or failures in the system. |
| Interface |
A shared boundary between various systems or programs. An
interface is also the equipment or device that makes it possible
to interoperate two systems. For example, it is common to interface
the 911 telephone system with a computer-aided dispatch (CAD)
system. Both hardware and software are needed to provide that
interface. |
| Ionosphere |
The band of charged particles 80 to 120 miles above the earth's
surface, which represent a nonhomogeneous and dispersive medium
for radio signals. |
| Ionospheric Delay |
A wave passing through the ionosphere is held up or "delayed"
for various reasons. Phase delay depends on the electron content
of the atmosphere and therefore this affects the carrier signals.
Group delay additionally depends on dispersion in the ionosphere
and this affects signal modulation (code signals). The phase
and group delay are of the same magnitude but opposite sign.
In practice ionospheric disturbance such as delays can affect
the accuracy of GPS measurements when measuring at long range. |
| Ionospheric refraction |
The change in the propagation speed of a signal as it passes
through the ionosphere. |
| IVHS |
Intelligent Vehicle Highway System |
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