Sony NV-U70 User Manual - Page 87
Glossary
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User's manual Sony Personal Navigation System Glossary COM-port GMT GPS HDOP POI Points of Interest 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 (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 Because of the Earth's uneven speed in its elliptic orbit, GMT has been replaced by UTC (Universal Time Coordinated) which is an ultra stable time standard based on atomic clocks. 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. 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. Point of Interest (POI). See ÎPoints 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. Glossary - 85 -