1. A SEMINAR ON PREPARED BY: MODHAVADIYA ARBHAM J. ROLL NO: 6553
SEM:-5th [C.E.]
L.D.C.E.

2. Where we are????

3. Today:- What GPS in past ? :- In the past, humans had to go to pretty
extreme measures to keep from getting lost.
For centuries, only way to navigate was to look
at position of sun and stars.
"artificial star"
Today:-
Sputnik on Oct. 4, 1957
Things are much, much easier today.
For less than $100, you can get a pocket-sized 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.

4. HISTORY First GPS satellite was called GPS block-I launched in 1978.
Basic purpose was for defence.
System of 24-satellites was achieved in 1994.

5. GPS ? :-
GPS: Global Positioning System is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations.
A simplistic explanation:
GPS uses these “man-made
stars” as reference points to
calculate positions accurate
to a matter of meters.

6. GPS SEGMENTS

7. GPS Communication and Control

8. Space segment GPS constellation. 24 satellite vehicles
Six orbital planes
Inclined 55o with respect to equator
Orbits separated by 60o
20,200 km elevation above Earth
Orbital period of 11 hr 55 min
Five to eight satellites visible from any point on Earth

9. GPS Ground Control Stations

10. Control station on the earth

11. The User Segment. U.S. Military Civilian shipping
Scientific high accuracy applications
Resource managers (GIS data capture)
Survey and mapping control

12. WORKING OF GPS

13. GPS Satellite Signal Structure
L1 Signal
L1 Carrier MHz
C/A-code MHz
Nav/System Data 50Hhz
P-Code MHz
L2 Signal
Mixer
Modulo 2 Sum

14. GPS Satellite Signal Structure.
Fundamental
Frequency
10.23 MHz
*154
L1 Carrier
MHz
C/A-code
1.023 MHz
P-Code
10.23 MHz
*120
L1 Carrier
MHz No
C/A-code
P-Code
10.23 MHz
Navigation 50 bps

15. Triangulation Position is calculated from distance measurement
Mathematically we need four satellites but three are sufficient by rejecting the ridiculous answer

16. Trilateration from satellites to determine position
Satellite positions in space are known

17. Measuring the distance to a satellite
Determination of the “pseudo” range is done by measuring travel time of GPS radio signals traveling at the speed of light.

18. Pseudo Range Trilateration
distance =
Elapsed time x 186,000 miles
per second

19. The distance (x) from one satellite tells us we're located somewhere on the surface of an imaginary sphere centered on that satellite with a radius of x.
x miles

20. Distance measurements from two satellites limits our location to the intersection of two spheres, which is a circle.

21. A third measurement narrows our location to just two points.

22. A fourth measurement determines which point is our true location

23. ACCURACY
The GPS receivers are extremely accurate due to its multi channel design.
Its time signals are too much accurate.
There is a difference of around15 meters from the object

24. Increasing GPS Accuracy through Differential Correction
Rover or Remote
(unknown)
Base Station (known)

25. ADVANTAGES GIS (Geographic Information System ) conversion is simple
Data collection costs are lower
Feature visual inspection is possible
while gathering data
Data gathering is possible 24-hours any time and any where
Unaffected by weather

26. DISADVANTAGES Requires training and retraining as technology changes
Buildings can block satellite signals
Heavy foliage and thick branched trees can attenuate and/or block satellite signals
Requires careful attention to system

27. APPLICATIONS OF GPS
DEFENCE
GEOLOGICAL SURVEY
AUTOMOBILES

28. DEFENCE
AIRFORCE
ARMY
NAVY

29. AUTOMOBILES

30. CURRENT RESEARCH & FUTURE DEVELOPMENTS
Earthquake monitoring
GPS management & technological
innovations will make GPS surveying easier & accurate
GPS is poised to become most revolutionary positioning technique of new century
Soon use it like cell-phone.

31. CONCLUSION

32. QUERIES

33. Thanks for your interest in the Global Positioning System