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Applications software satisfies your specific need. The developers of
application software rely mostly on marketing research strategies trying to do their
best to attract more users (buyers) to their software. As the productivity of the
hardware has increased greatly in recent years, the programmers nowadays tend to
include as much as possible in one programme to make software interface look more
attractive to the user. These class of programmes is the most numerous and
perspective from the marketing point of view. Data communication within and
between computers systems is handled by system software. Communications
software transfers data from one computer system to another. These programmes
usually provide users with data security and error checking along with physically
transferring data between the two computer's memories. During the past five years
the developing electronic network communication has stimulated more and more
companies to produce various communication software, such as Web-Browsers for
Internet.
Текст 4
WHAT IS GPS?
The Global Positioning System (GPS) is a satellite-based navigation system
made up of a network of 24 satellites. GPS was originally intended for military
applications, but now the systems is available for civilian use. GPS works in any
weather conditions, anywhere in the world, 24 hours a day.
GPS satellites circle the earth twice a day in a very precise orbit and transmit
signal information to Earth. GPS receivers take this information and use triangulation
to calculate the user's exact location. Essentially, the GPS receiver compares the time
a signal was transmitted by a satellite with the time it was received. The time
difference tells the GPS receiver how far away the satellite is. Now, with distance
measurements from a few more satellites, the receiver can determine the user's
position and display it on the unit's electronic map.
A GPS receiver must be locked on to the signal of at least three satellites to
calculate a 2D position (latitude and longitude) and track (прослеживать) movement.
With four or more satellites in view, the receiver can determine the user's 3D position
(latitude, longitude and altitude). Once the user's position has been determined, the
GPS unit can calculate other information, such as speed, bearing (пеленг), track, trip
distance, distance to destination, sunrise and sunset time and more.
Today's GPS receivers are extremely accurate within an average of three to five
meters thanks to their parallel multi-channel design.
The 24 satellites that make up the GPS space segment are orbiting the earth
about 12,000 miles above us. They are constantly moving, making two complete
orbits in less than 24 hours. These satellites are travelling at speeds of roughly 7,000
miles an hour.
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