User`s guide

Appendix
Motorola GPS Products - M12+ User's Guide Revision 6.X 09FEB05
204
GPS ICD-200
The GPS Interface Control Document is a government document that contains
the full technical description of the interface between the satellites and the user. GPS
receivers must comply with this specification if they are to receive and process GPS
signals properly.
Gravitational Constant
The proportionality constant in Newton's Law of Gravitation.
G = 6.672 x 10
11
Nm
2
/Kg
2
.
Greenwich Mean Time (GMT)
See Universal Time.
HDOP
Horizontal dilution of precision. See Dilution of Precision.
Hot Start
Typical time a GPS receiver requires to develop a fix after application of power given that
the receiver has stored time, position, almanac data, and ephemeris data.
HOW
Handover Word. The word in the GPS message that contains time synchronization
information for the transfer from the C/A code to the P code. Refer to GPS ICD-200 for
details.
Inclination
The angle between the orbital plane of a body and some reference plane (e.g. equatorial
plane).
INS
Inertial Navigation System, which contains an Inertial Measurement Unit (IMU).
Integer Bias Terms
The receiver counts the radio waves from the satellite, as they pass its antenna, to a high
degree of accuracy. However, it has no information on the number of waves to the
satellite at the time it started counting. This unknown number of wavelengths between the
satellite and the antenna is the integer bias term.
Integrated Doppler
A measurement of Doppler shift frequency or phase over time.
Ionospheric Delay
A wave experiences delay while propagating through the ionosphere, which is non-
homogeneous in space and time and is a dispersive medium. Phase delay depends on
electron content and affects carrier signals. Group delay depends on dispersion in the
ionosphere as well, and affects signal modulation (codes). The phase and group delay
are of the same magnitude, but opposite sign.