08-06-2013, 11:10 AM
Global positioning system
[attachment=54977]
INTRODUCTION
Have u ever been lost and wished there was an easy way to find out which way u
needed to go? How about finding yourself out hiking and then not knowing how
to get back to your camp or car? Ever been flying and wanted to know the
nearest airport?
Our ancestors had to go to pretty extreme measures to keep from getting lost.
They erected monumental landmarks, laboriously drafted detailed maps and
learned to read the stars in the night sky.
GPS is a satellite based radio navigation system which provides continuous, all
weather, worldwide navigation capability for sea, land and air applications. So
things are much, much easier today. For less than $100, you can get a pocketsized
gadget that will tell you exactly where you are on Earth at any moment. As
long as you have a GPS receiver and a clear view of the sky, you'll never be lost
again.
Navigation in three dimensions is the primary function of GPS. Navigation
receivers are made for aircraft, ships, ground vehicles, and for hand carrying by
individuals. Precise positioning is possible using GPS receivers at reference
locations providing corrections and relative positioning data for remote
receivers. Surveying, geodetic control, and plate tectonic studies are examples.
Time and frequency dissemination, based on the precise clocks on board the SVs
and controlled by the monitor stations, is another use for GPS. Astronomical
observatories, telecommunications facilities, and laboratory standards can be set
to precise time signals or controlled to accurate frequencies by special purpose
GPS receivers.
THE GPS EVOLUTION
GPS, which stands for Global Positioning System, is the only system today able
to show you your exact position on the Earth anytime. The Global Positioning
System is a constellation of satellites that orbit the earth twice a day, transmitting
precise time and position (latitude, longitude and altitude) information.
Cavemen probably used stones and twigs to mark a trail when they set out
hunting for food. The earliest mariners followed the coast closely to keep from
getting lost. When navigators first sailed into the open ocean, they discovered
they could chart their course by the stars. The next major developments in the
quest for the perfect method of navigation were the magnetic compass and the
sextant. The needle of a compass always points north, so it is always possible to
know in what direction you are going. The sextant uses adjustable mirrors to
measure the exact angle of the stars, moon, and sun above the horizon. GPS is
one of the most fantastic utilities ever devised by man. GPS will figure in history
alongside the development of the sea-going chronometer. This device enabled
seafarers to plot their course to an accuracy that greatly encouraged maritime
activity, and led to the migration explosion of the nineteenth century. GPS will
affect mankind in the same way. There are myriad applications that will benefit
us individually and collectively.
WHAT IS GPS?
The Global Positioning System (GPS) is a
satellite-based navigation system made up of a
network of 24 satellites placed into orbit by
the U.S. Department of Defense that
continuously transmit coded information,
which makes it possible to precisely identify
locations on earth by measuring the distance
from the satellites. The satellites transmit very
low power specially coded radio signals that
can be processed in a GPS receiver, enabling the receiver to compute position,
velocity and time thus allowing anyone one with a GPS receiver to determine
their location on earth. Four GPS satellite signals are used to compute positions
in three dimensions and the time offset in the receiver clock. The system was
designed so that receivers did not require atomic clocks, and so could be made
small and inexpensively.
PRINCIPLE OF GPS
The principle behind GPS is the measurement of distance (or "range") between
the receiver and the satellites. The satellites also tell us exactly where they are in
their orbits above the Earth. It works something like this-If we know our exact
distance from a satellite in space, we know we are somewhere on the surface of
an imaginary sphere with radius equal to the distance to the satellite radius. By
measuring its distance from a second satellite, the receiver knows it is also
somewhere on the surface of a second sphere with radius equal to its distance
from the second satellite. Therefore, the receiver must be somewhere along a
circle which is formed from the intersection of the two spheres. Measurement
from a third satellite introduces a third sphere. Now there are only two points
which are consistent with being at the intersection of all three spheres. One of
these is usually impossible, and the GPS receivers have mathematical methods
of eliminating the impossible location. Measurement from a fourth satellite now
resolves the ambiguity as to which of the two points is the location of the
receiver. The fourth satellite point also helps eliminate certain errors in the
measured distance due to uncertainties in the GPS receiver's timing as well.
[attachment=54977]
INTRODUCTION
Have u ever been lost and wished there was an easy way to find out which way u
needed to go? How about finding yourself out hiking and then not knowing how
to get back to your camp or car? Ever been flying and wanted to know the
nearest airport?
Our ancestors had to go to pretty extreme measures to keep from getting lost.
They erected monumental landmarks, laboriously drafted detailed maps and
learned to read the stars in the night sky.
GPS is a satellite based radio navigation system which provides continuous, all
weather, worldwide navigation capability for sea, land and air applications. So
things are much, much easier today. For less than $100, you can get a pocketsized
gadget that will tell you exactly where you are on Earth at any moment. As
long as you have a GPS receiver and a clear view of the sky, you'll never be lost
again.
Navigation in three dimensions is the primary function of GPS. Navigation
receivers are made for aircraft, ships, ground vehicles, and for hand carrying by
individuals. Precise positioning is possible using GPS receivers at reference
locations providing corrections and relative positioning data for remote
receivers. Surveying, geodetic control, and plate tectonic studies are examples.
Time and frequency dissemination, based on the precise clocks on board the SVs
and controlled by the monitor stations, is another use for GPS. Astronomical
observatories, telecommunications facilities, and laboratory standards can be set
to precise time signals or controlled to accurate frequencies by special purpose
GPS receivers.
THE GPS EVOLUTION
GPS, which stands for Global Positioning System, is the only system today able
to show you your exact position on the Earth anytime. The Global Positioning
System is a constellation of satellites that orbit the earth twice a day, transmitting
precise time and position (latitude, longitude and altitude) information.
Cavemen probably used stones and twigs to mark a trail when they set out
hunting for food. The earliest mariners followed the coast closely to keep from
getting lost. When navigators first sailed into the open ocean, they discovered
they could chart their course by the stars. The next major developments in the
quest for the perfect method of navigation were the magnetic compass and the
sextant. The needle of a compass always points north, so it is always possible to
know in what direction you are going. The sextant uses adjustable mirrors to
measure the exact angle of the stars, moon, and sun above the horizon. GPS is
one of the most fantastic utilities ever devised by man. GPS will figure in history
alongside the development of the sea-going chronometer. This device enabled
seafarers to plot their course to an accuracy that greatly encouraged maritime
activity, and led to the migration explosion of the nineteenth century. GPS will
affect mankind in the same way. There are myriad applications that will benefit
us individually and collectively.
WHAT IS GPS?
The Global Positioning System (GPS) is a
satellite-based navigation system made up of a
network of 24 satellites placed into orbit by
the U.S. Department of Defense that
continuously transmit coded information,
which makes it possible to precisely identify
locations on earth by measuring the distance
from the satellites. The satellites transmit very
low power specially coded radio signals that
can be processed in a GPS receiver, enabling the receiver to compute position,
velocity and time thus allowing anyone one with a GPS receiver to determine
their location on earth. Four GPS satellite signals are used to compute positions
in three dimensions and the time offset in the receiver clock. The system was
designed so that receivers did not require atomic clocks, and so could be made
small and inexpensively.
PRINCIPLE OF GPS
The principle behind GPS is the measurement of distance (or "range") between
the receiver and the satellites. The satellites also tell us exactly where they are in
their orbits above the Earth. It works something like this-If we know our exact
distance from a satellite in space, we know we are somewhere on the surface of
an imaginary sphere with radius equal to the distance to the satellite radius. By
measuring its distance from a second satellite, the receiver knows it is also
somewhere on the surface of a second sphere with radius equal to its distance
from the second satellite. Therefore, the receiver must be somewhere along a
circle which is formed from the intersection of the two spheres. Measurement
from a third satellite introduces a third sphere. Now there are only two points
which are consistent with being at the intersection of all three spheres. One of
these is usually impossible, and the GPS receivers have mathematical methods
of eliminating the impossible location. Measurement from a fourth satellite now
resolves the ambiguity as to which of the two points is the location of the
receiver. The fourth satellite point also helps eliminate certain errors in the
measured distance due to uncertainties in the GPS receiver's timing as well.