Si-tex GPS-95CP, Руководство пользователя

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GPS
Fix Text Below, so that Words Do Not Separated Strangely at End of each
Line.
For centuries, sailors have been searching for a reliable and precise method of travelling the wor
ld’s waterways. From celestial navigating to the modern navigation techniques as Loran, Decca
navigator, Omega or Transit Satnav, each system has had its problems with weather, range and
reliability. Without doubt, the “Global Positioning System”, or GPS for short, is the most significa
nt advance in navigation: it provides the navigator a position 24 hours a day, 365 days a year in
any weather condition.
GPS is a satellite based navigation system which provides suitably equipped users with accur
ate position, velocity and time data. Originally the GPS, developed by the U.S. Department of De
fense, was conceived for military purposes, but now it is used in a host of civilian applications.
GPS navigation uses satellite signals to determine your position in relation to a set of satellites o
rbiting the earth. The GPS constellation of satellites continuously sends radio signals, containing
the precise position for each satellite back to earth. By knowing the position of 3 or 4 satellites
and calculating various time differences between transmitted signals, the GPS receiver can deter
mine its present position anywhere on earth, and thanks to continuous updates, calculate speed
and course information.
HOW GPS WORKS
Currently, the GPS constellation consists of 26 orbiting satellites (including 3 spares), but this n
umber will increase in the future.
The GPS receiver computes an accurate position by calculating the distance to the GPS satellite
s that orbit the earth. Signals are required from 3 satellites for two dimensional (2D) position cal
culation whilst 4 satellites are required for three dimensional (3D) position calculation.
As mentioned earlier, GPS satellites are not geostationary, but they are orbiting the earth as illust
rated on the following figure:
[The GPS constellation]
Note that position is repeatedly fixed through the following three steps while any 3 satellites are i
n line of sight.