NAVIOR-24S
™
Appendix G
Glossary
226
NAVIOR-24S ™
Revision
V1.00 20.05.2008
constellation switch is only active when the GPS mode of operation is
set to Auto.
PRN
Pseudo-random noise. Each GPS satellite generates its own distinctive
PRN code, which is modulated onto each carrier. The PRN code serves
as identification of the satellite, as a timing signal, and as a subcarrier
for the navigation data.
protocol
A formal set of rules that describe a method of communication. The
protocol governs the format and control of inputs and outputs.
pseudo-range
A measure of the range from the GPS antenna to a GPS satellite.
Pseudo-range is obtained by multiplying the speed of light by the
apparent transit time of the signal from the GPS satellite. Pseudo-range
differs from actual range because the satellite and user clocks are offset
from GPS time and because of propagation delays and other errors
RAM Random-Access
Memory
random-access memory Memory in which information can be referred to in an arbitrary or
random order. The contents of RAM are lost when the System Unit is
turned off
range
A term used to refer to the distance radio signals can travel before they
must be received or repeated due to loss of signal strength, the curvature
of the earth and the noise introduced because of moisture in the air
surrounding the earth's surface.
range rate
The rate of change of range between the satellite and receiver. The
range to a satellite changes due to satellite and observer motions. Range
rate is determined by measuring the Doppler shift of the satellite beacon
carrier.
read-only memory
Memory whose contents can be read, but not changed. Information is
placed into ROM only once. The contents of ROM are not erased when
the system unit's power is turned off.
real time clock
An electronic clock, usually battery powered, that keeps current time.
Used by a GPS receiver during a warm or hot start to determine where
to search for GPS satellite signals.
Relative positioning
The process of determining the vector distance between two points and
the coordinates of one spot relative to another. This technique yields
GPS positions with greater precision than a single point positioning
mode can.
rise/set time
Refers to the period during which a satellite is visible; i.e., has an
elevation angle that is above the elevation mask. A satellite is said to
“rise” when its elevation angle exceeds the mask and “set” when the
