Transcript GLOBAL POSITIONING SYSTEM GPS)

PRESENTATION BASED ON
GPS
Introduction
To GPS
• GPS is a spaced based radio
positioning system, which provide
suitably equipped user with highly
accurate position, velocity and time data
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GPS provide specially coded signals that
can be processed in a GPS receiver.
A GPS receiver decodes time signal
transmission from multiple satellites and
calculated its position.
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GPS system was designed & controlled by
US military.
The cost of maintaining the system is
approximately US $400 million per year
including the replacement of aging
satellite.
Earth
Circumference
 24,900 Miles
Rotation
 1,038
Miles/Hour
 1 Day Cycle
Moon
1/4 Size of the
Earth
Distance from
Earth
239,000 Miles
The History of GPS
Feasibility studies begun in 1960’s.
 Pentagon appropriates funding in
1973.
 First satellite launched in 1978.
 System declared fully operational
in April, 1995.
 Open to the public, 2000.
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How does GPS work?
 Stations
on earth, and a GPS
receiver, the distances between
each of these points can be
calculated.
 The
distance is calculated based
on the amount of time it takes for
a radio signal to travel between
these points.
 Using
satellites in the sky,
ground allows the GPS receiver
to know where you are, in terms
of latitude and longitude, on the
earth.
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The more satellites the GPS can “see”, the more accurate your reading.
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The GPS must “see” the satellites, so it does not work well in dense
forests, inside caves, underwater, or inside buildings.
GPS Satellites
Distance from
Earth
12,000 Miles
2 Orbits in 24
Hours
Travel 7,000
MPH
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Satellites Segments
Three major segment of GPS
system
Space segment
 Control segment
 User segment
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Space segment :
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A space segment contain 24 satellites.
The satellite arranged such that a
minimum of four satellite is in view to a
user at any time on a world wide basis.
Each satellite transmits signals on two
radio frequencies, superimposed on which
are navigation and system data.
The satellite orbit in six separate orbital
planes.
Slide 28
 24 satellites in six orbital
plane
 12,000 miles above Earth
 Orbit twice daily
 At least 4 satellites in
view
 Distance from Earth to
Moon - 256,000 miles
 4 satellite in each plane
 20,200 km altitude 55
degree inclination.
Control Segment
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The control segment includes a master
control station(MCS).
A number of monitor stations, and ground
antennas throughout the world.
The master control station, located in
Colorado Springs.
Colorado consists of equipment and
facilities required for satellite monitoring,
tracking, commanding, control, uploading,
and navigation message generation.
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User
Segment
Military.
Search and rescue.
Disaster relief.
Surveying.
Marine, aeronautical and terrestrial navigation.
Remote controlled vehicle and robot guidance.
Satellite positioning and tracking.
Shipping.
Geographic Information Systems (GIS).
Recreation.
What does a GPS receiver do?
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GPS receiver allows you to pinpoint your
location, anywhere in the world, based on
latitude and longitude coordinates.
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It can tell you in what direction you are heading.
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It can show you:
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how fast you are going
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your altitude
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a map to help you arrive at a destination
Signal From One Satellite
The receiver is
somewhere on
this sphere.
Signals From Two Satellites
Three Satellites
(2D Positioning)
Three Dimensional
(3D) Positioning
How GPS Works
Ok, you’re lost, you have
amnesia, and you have
absolutely no idea where you
are. You go up to someone,
and like a good amnesiac
you ask, “Where Am I?” This
person tells you that you are
625 miles from Boise, Idaho.
You say, sarcastically, “Wow,
that’s some great
information. Thanks Buddy.”
We’re Getting Closer
You still have absolutely no
idea where you are, so once
again you go up to someone
and ask, “Where Am I?” This
person tells you that you’re
690 miles from Minneapolis.
You just scratch your head,
but then you start to
remember what you learned in
GPS class, and, with the US
map in your pocket to guide
you, you proceed.
Now We Know!
You see a another smiling face
and ask “where am I” one
more time. This time you get
the reply “you are 615 miles
from Tucson. The light pops
on in your brain. It’s all clear
now. You draw three circles
extending in the radii of 625
miles from Boise, 690 from
Minneapolis, and 615 miles
from Tucson. The circles
intersect in Denver! Aren’t you
glad that you took this class?
GPS by Trilateration
GPS Distance D = Speed of Light x Time;
or D = CT
D
Waypoint
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A waypoint is based on coordinates entered
into a GPS receiver’s memory.
It can be either a saved position fix, or user
entered coordinates.
It can be created for any remote point on earth.
It must have a receiver designated code or
number, or a user supplied name.
Once entered and saved, a waypoint remains
unchanged in the receiver’s memory until
edited or deleted.