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Introduction To

G.P.S.
Contents
What is GPS
The need for positioning system
Segments of GPS
• Space Segment
• Control segment
•Users Segment
...
What is GPS ??
GPS, which stands for Global
Positioning System, is the only
system today able to show you your
exact posit...
The need for positioning system
From the beginning of civilization, people
wanted to know where they are or how to go to
...
GPS can tell you where you are
Developed and maintained by the US
Department of Defense (DOD)
 Satellite Based
 24 sate...
Segments of GPS
1. Space Segment
A constellation of 24 satellites

2. Control segment
A network of earth-based facilities
...
SPACE SEGMENT


24 satellite vehicles



6 obital planes



Obital period of 11 hr 55 min



20,200 km elevation above...
CONTROL SEGMENT


Monitor and control GPS satellites



One master control station (MCS)



Five monitor stations



T...
GPS Monitoring Station
User Segment
• Receive signal from satellites
• calculate current position and speed/direction
How GPS Works ………
Uses measurements from 4+ satellites
Distance = travel time x speed of light
Time Difference
•The GPS receiver compares the time
a signal was transmitted by a satellite
with the time it was received....
Calculating Distance
Velocity x Time = Distance
Radio waves travel at the speed of light, roughly 186,000
miles per second...
TRIANGULATION
• Suppose

+ A
Satellite
+

Satellite B

Satellite A to our position
is 11,000 miles
• At this point we coul...
Determining GPS Position
+

Satellite A

+

Satellite B

+ C
Satellite

•Taking another measurement from a 3rd
satellite n...
GPS for Navigation
Applications of GPS
Military Applications
• Digital Assistant for soldiers
(personal navigation)
• Search and rescue missi...
Civilian Applications
• Vehicle navigation (for cars, airplanes, and ships)
- Use GPS to determine position, speed, and di...
Civilian Applications
• Used in map-making and land
surveying

• Various usages in many fields of
industry
• Outdoor Activ...
Civilian Applications
• Location-based service (LBS), Social Network Service (SNS)
- Finding the location of family or fri...
References
• http://www.howstuffworks.com/gps.htm
•http://www.howstuffworks.com/38how-gps-works-video.htm
• http://en.wiki...
Global positioning system
Global positioning system
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Global positioning system

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Global positioning system

  1. 1. Introduction To G.P.S.
  2. 2. Contents What is GPS The need for positioning system Segments of GPS • Space Segment • Control segment •Users Segment  How GPS Works TRIANGULATION Applications of GPS
  3. 3. What is GPS ?? GPS, which stands for Global Positioning System, is the only system today able to show you your exact position on the Earth anytime, in any weather, anywhere. Full name : NAVSTAR GPS - NAVigation Satellite Time And Ranging Global Positioning System
  4. 4. The need for positioning system From the beginning of civilization, people wanted to know where they are or how to go to somewhere. Ancient sailors used wind and stars to get the direction. Also people have been using compass, map, and other methods to know their location and direction.
  5. 5. GPS can tell you where you are Developed and maintained by the US Department of Defense (DOD)  Satellite Based  24 satellites  20,200 km high orbit  Six orbital planes with four satellites each  55 inclination with equator
  6. 6. Segments of GPS 1. Space Segment A constellation of 24 satellites 2. Control segment A network of earth-based facilities 3. Users Segment
  7. 7. SPACE SEGMENT  24 satellite vehicles  6 obital planes  Obital period of 11 hr 55 min  20,200 km elevation above Earth  Five to eight satellites visible from any point on Earth
  8. 8. CONTROL SEGMENT  Monitor and control GPS satellites  One master control station (MCS)  Five monitor stations  Three ground antennas
  9. 9. GPS Monitoring Station
  10. 10. User Segment • Receive signal from satellites • calculate current position and speed/direction
  11. 11. How GPS Works ……… Uses measurements from 4+ satellites Distance = travel time x speed of light
  12. 12. Time Difference •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.
  13. 13. Calculating Distance Velocity x Time = Distance Radio waves travel at the speed of light, roughly 186,000 miles per second (mps) If it took 0.06 seconds to receive a signal transmitted by a satellite floating directly overhead, use this formula to find your distance from the satellite. 186,000 mps x 0.06 seconds = 11,160 miles
  14. 14. TRIANGULATION • Suppose + A Satellite + Satellite B Satellite A to our position is 11,000 miles • At this point we could be located anywhere on the specified sphere • Next, let us take another measurement from a second satellite, Satellite B •Now our position is narrowed down to the intersection of theses two sphere
  15. 15. Determining GPS Position + Satellite A + Satellite B + C Satellite •Taking another measurement from a 3rd satellite narrows our position down even further, to the two points • These points are located where the 3rd sphere cuts through the intersection of first two spheres •So by ranging from 3 satellites we can narrow our position to just two points in space •We could make a 4th measurement from another satellite to determine the true point • Or, We can eliminate one of the two points that gives a point which may be too far from the earth • However, GPS receivers use a 4th satellite to precisely locate our position
  16. 16. GPS for Navigation
  17. 17. Applications of GPS Military Applications • Digital Assistant for soldiers (personal navigation) • Search and rescue missions • Detect nuclear detonation with sensors on satellites (optical sensor, X-ray sensor, EMP sensor, etc..)
  18. 18. Civilian Applications • Vehicle navigation (for cars, airplanes, and ships) - Use GPS to determine position, speed, and direction
  19. 19. Civilian Applications • Used in map-making and land surveying • Various usages in many fields of industry • Outdoor Activities (Hike/bike trails, GeoCaching)
  20. 20. Civilian Applications • Location-based service (LBS), Social Network Service (SNS) - Finding the location of family or friend - Integrate current location with social network - Using GPS-enabled phones (mostly smart phones)
  21. 21. References • http://www.howstuffworks.com/gps.htm •http://www.howstuffworks.com/38how-gps-works-video.htm • http://en.wikipedia.org/

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