Sony NV-U50 - Manual (Page 87)

User's manual Sony Personal Navigation System
Glossary - 85 -
Glossary
COM-port A COM port is a connector to a communications interface, usually
the serial port. The ports are numbered by a number behind
"COM". A communications interface is designed to connect
hardware like a mouse or a GPS receiver.
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orbit, GMT has been replaced by UTC (Universal Time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 ÎPoints of Interest.
Points of Interest Points of Interest, also called POI, are covered by the map and
may be displayed on it. Harbors, airports, restaurants, hotels,
petrol stations, public buildings, and others belong to the points
of interest. You may determine points of interest as itinerary
points for navigation purposes.