NAVIOR-24S
™
Appendix G
Glossary
225
NAVIOR-24S ™
Revision
V1.00 20.05.2008
occurrences on communication channels that are a result of natural or
man-made noises and signals, not properly a part of the signals being
transmitted or received.
Integrated Doppler
A measurement of Doppler shift frequency or phase over time
IODE
Issue Of Data, Ephemeris. Part of the navigation data. It is the issue
number of the ephemeris information. A new ephemeris is available
usually on the hour. Especially important for Differential GPS operation
that the IODE change is tracked at both the reference station and mobile
stations.
jamming
Interference (in either transmitting or receiving signals) caused by other
radio signals at exactly or approximately the same frequency.
Kalman filter
A numerical method used to track a time-varying signal in the presence
of noise. If the signal can be characterized by some number of
parameters that vary slowly with time, then Kalman filtering can be
used to tell how incoming raw measurements should be processed to
best estimate those parameters as a function of time.
masks See
satellite
masks
maximum PDOP
A measure of the maximum Position Dilution of Precision (PDOP) that
is acceptable in order for the GPS processor to determine a location
solution (see PDOP)
NAVSTAR
The name given to the GPS satellites, built by Rockwell International,
which is an acronym formed from NAVigation System with Time And
Ranging.
NMEA National
Marine
Electronics Association. An association that defines
marine electronic interface standards for the purpose of serving the
public interest
NMEA 0183 message
NMEA 0183 is a standard for interfacing marine electronics
navigational devices. The standard specifies the message format used to
communicate with marine devices/components.
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
