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Acutime 2000 Synchronization Kit User Guide Glossary-9
Glossary
packet An "envelope" for data, which contains addresses and error
checking information as well as the data itself.
parity A scheme for detecting certain errors in data transmission.
Parity defines the condition (i.e., even or odd) of the number
of items in a set (e.g., bits in a byte).
PDOP Position Dilution of Precision. PDOP is a unitless figure of
merit that describes how an uncertainty in pseudo-range
affects position solutions.
PDOP
constellation
switch
A value, based on PDOP, that defines when the GPS
receiver/processor should switch between 2-D and 3-D GPS
modes. The PDOP 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.