WITH THIS SLIDE YOU ALL WILL BE ABLE TO GAIN CONCEPT ON GPS.,YOU WILL ABLE TO CLEAR YOUR CONCEPT..ON MANY PROJECTS RELATED TO..GPS ..
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2. Overview
What is GPS?
What does the GPS do?
How it works
GPS codes
Application with GPS
Pocket Street
Farming
agriculture
Automated Vehicle Location System
3. Global Positioning System
(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.
GPS satellites
24 Satellites in 6 planes, each
plane has 4 satellites
These space vehicles (SVs)
send radio signals from space.
4. What does the GPS do
Satellite signals can be
processed in a GPS receiver.
GPS receiver will show your
EXACT location on the Earth
(latitude and longitude)
Helps you find your way to a
specified location
Let’s you know what direction
you are heading and how fast
you are going
5. GPS- How it works
Measuring the distance from a satellite by measuring
travel time of radio signals seconds
Distance = speed of light * latency in time
Four GPS satellite signals are used to compute positions
in three dimensions and the time offset in the receiver
clock.
6. GPS- How it works
Given 1 satellite …
We can locate our
position on the
surface of a sphere
7. With two satellites you could narrow your
location down to two possible locations.
You Could Be
Here?
NEXT
8. With three satellites you could get a better estimate
on your location. It would narrow it down to one
point.
YOU ARE
HERE
NEXT
10. “”
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.
With four or more satellites in view, the receiver can
determine the user's 3D position (latitude, longitude and
altitude).
11. When GPS receives a signal
It compares that signal with all the known codes
(there are currently 37).
The receiver determines which satellite it is.
It decodes the timing information, multiplies by
the speed of light to find the radius of the
sphere.
Once it has done that for 3 satellites, it can
determine the location.
12. How do GPS signals send all
this information?
They use codes! Binary codes.
Each satellite has a different code.
14. Strategy
First we need to learn how GPS creates
these codes
Then we need to come up with a way to
quickly tell the codes apart.
15. How do you create codes?
You use binary addition rules.
0+0=0
1+0=1
0+1=1
1+1=10 (but only use the last bit, 0)
GPS uses “shift registers.”
The more shift registers you have, the more
complicated you can make your code.
16. Register1 Register2 Register3 Code
1 1 1 -
Start with all 1’s in your shift registers
Add Register 1 and Register 3
The answer 0 goes into Register 1 and
everything shifts to the right.
Here is an example with 3 shift registers
For this example, 1+1 =10 ==> 0
17. After 2N -1 steps (N is the number of
registers), the code repeats
Register1 Register2 Register3 Code
1 1 1 -
0 1 1 1
1 0 1 1
0 1 0 1
0 0 1 0
1 0 0 1
1 1 0 0
1 1 1 0
For 3 shift registers, the code repeats after 7 steps.
18. Real GPS
Uses 10 shift registers.
They add different registers to produce the
codes for different satellites.
Satellite 1 uses 2 and 6.
Satellite 2 uses 3 and 7, and so on.
A 10-shift register code repeats after 210-1,
or 1023.
19. How do you compare codes?
100111101110100010011011111111101
000010001010011100001110010010001
Every time the numbers agree, add 1.
Every time the numbers disagree, subtract 1.
20. This example: 2 different satellites
100111101110100010011011111111111
000010001010011100001110010010001
14 agree
11 disagree
Total score: 3
Perfect agreement would be 35
21. Why are the codes shifted? The shift gives the
GPS receiver the time difference.
Time Difference (in seconds) * 2.99792458 108 meters/second =
Distance (in meters)
What is a typical Time Difference? GPS
satellites are ~20,000,000 meters above
the Earth.
20,000,000/300,000,000~ 70 milliseconds
22. Pocket Streets- an example with
GPS
Pocket Streets offers exciting
features such as street-smart
mapping, map customization,
GPS and Microsoft Outlook
integration.
With Pocket Streets on your
Pocket PC, you will take a smart
map with you wherever you go.
23. Pocket Streets- an example with
GPS
Download the map for the city.
Connect the GPS receiver to
Pocket PC.
Choose "Track Position" from the
GPS menu to show your current
position on the map.
The position moves when you move.
24. Farming
Farmers can use GPS
to help them plow
very straight rows
to enable them use
their land more
efficiently.
NEXT
25. Agriculture
Farmers can use GPS to help
mark areas for pesticide or
fertilizer application. Thus
reducing waste.
NEXT
26. Automated Vehicle Location
System
Where is the bus
What direction is
the bus traveling to
What is the travel
speed
Where is stop
How long is the stop
27. Automated Vehicle Location
System
How Do GPS Relate?
GPS receiver calculates its position (latitude and
longitude) and record the information at fixed time
interval
GPS transmitter transmits location and vehicle
dynamic data to control center at prescribed interval
Control center system process data accoding to
customer specifications
29. Applications – Military
Military GPS user equipment has been
integrated into fighters, bombers, tankers,
helicopters, ships, submarines, tanks,
jeeps, and soldiers' equipment.
To prevent GPS interception by the
enemy, the government controls GPS
receiver exports
30. Another GPS application?
Besides being used by the military, GPS is
used in forestry, biology, fishing, hunting,
boating, racing, nursing, and many other
fields.
GPS technology can be effectively used in
your classroom as well.
31. Conclusions
GPS can show your EXACT location on the Earth
(latitude and longitude)