User's Manual MobileNavigator|6
Glossary
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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orbit, GMT has been replaced by UTC (Universal Time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
which 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 altitude 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
may occur. The smaller the value, the more accurate is the
position determination (value 0 = no deviation from the real
position). Values up to 8 are convenient for navigation purposes.
POI
Point of Interest (POI). See: Special destination.
Special destination
Special destinations, also called POI (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.
