Pioneer AVIC-S1 - Manual (Page 119)

User's manual AVIC-S1
Glossary - 117 -
10 Glossary
GMT GMT (Greenwich Mean Time) is the mean solar time at the Royal
Greenwich Observatory in Greenwich near London, England,
which by convention is at 0 degrees geographic longitude.
Theoretically, noon Greenwich Mean Time is the moment when
the Sun crosses the Greenwich meridian (and reaches its highest
point in the sky in Greenwich). Up to 1972, GMT was the global
time standard. Because of the Earth's uneven speed in its elliptic
orbit, GMT has been replaced by UTC (Universal Time
Coordinated) which is an ultra stable time standard based on
atomic clocks.
GPS The GPS (Global Positioning System) is based on 24 satellites
that are in orbit round the earth. They are permanently emitting
the time and their current position. The GPS receiver receives
this information and calculates the longitude and the latitude of
its own current position.
The signals of at least three satellites are needed to determine
the longitude and the latitude. With the signals of at least four
satellites the elevation may be calculated, too. The determination
has an accuracy of about 3 yards.
HDOP The Horizontal Dilution of Precision (HDOP) indicates the quality
of position determination. Theoretically any value from 0 to 50 is
possible. The smaller the value is, the more accurate is the
position determination (value 0 = no deviation from the actual
position). Values up to 8 are convenient for street navigation.
POI Point of Interest (POI). See ÎPoint of Interest.
RDS Radio Data Signal (RDS) is a service offered by broadcasting
stations. TMC information is broadcasted via RDS.
Point of Interest Points of Interest are covered by the map and may be displayed
on it. Harbours, airports, restaurants, hotels, petrol stations,
public buildings, and others belong to the special destinations.
You may determine special destinations as itinerary points for
navigation purposes.
TMC Traffic Message Channel (TMC) supplies your navigation system
with the latest traffic information. A TMC module which is
available as accessory receives the signals which are broadcasted
by radio stations.