This is gos technology overview for military and educational purposes

2. GLOBAL POSITIONING
SYSTEM.

3. What is GPS?
The Global Positioning System

4. What is GPS?
GPS is a network of satellites that continuously
transmit coded information, which makes it
possible to precisely identify locations on earth
by measuring distance from the satellites.

6. THREE SEGMENTS OF GPS
Monitor stations
• Diego Garcia
• Ascension Island
• Kwajalein
• Hawaii
USER SEGMENT
SPACE SEGMENT
GPS Control
Colorado Springs
GROUND CONTROL SEGMENT

7. GPS - A Constellation of about 24
Navigation Satellites Orbiting the Earth
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8. GPS
GEN.
 GPS BASED ON A
CONSTELLATION OF - 24 SATLS.
 NO OF ACTIVE SATLS - 21
 NO OF ACTIVE RES - 3
 DIST OF ORBIT FROM
SURFACE OF EARTH - 20,233 KM
 NO OF ORBITS - 6
 SATL/ORBIT - 4

9. Space Segment Description
• 24 satellites
– 6 planes with 55° rotation
– Each plane has 4 or 5 satellites
• Very high orbit
– 20,200 km (12,600 miles)
– 1 revolution in
approximately 12 hours
– For accuracy
– Survivability
– Coverage

10. GROUND CONTROL SEGMENT
Monitor stations
• Diego Garcia
• Ascension Island
• Kwajalein
• Hawaii
GPS Control
Colorado Springs
NAVDATA - Satellite health,
satellite clock corrections,
and ephemeris parameters.
Ground Control Segment Monitors
Ephemeris
The position information
broadcast from the satellite is
referred to as the ephemeris.
The ephemeris contains precise
information about the satellite’s
orbit. Each satellite has an
ephemeris.

11. GROUND MONITORING STATIONS

12. USER SEGMENT
• HAND HELD GPS Receiver
• CAR GPS Receiver
• AIRCRAFT GPS Receiver
• DIFFERENTIAL GPS
ANTENNA
MICRO PROCESSOR
CONTROL & DISPLAY UNIT
RECORDING DEVICE
POWER SUPPLY

14. How is GPS technology used?
GPS is used to determine position
 Latitude, Longitude, Altitude
of an object
Applications range from naviation
to data collection for GIS/Mapping

15. What is GIS?
Geographic Information Systems
GIS allows us to create maps
GIS provides tools for analyzing
geographic information

16. CONCEPT OF OPERATION

17. Specifics on GPS Technology
- How GPS receiver calculates position
- How accurate is GPS
- What affects GPS accuracy

18. Not To Scale!
GPS receiver tracks satellites and uses
trilateration to calculate its position
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19. Not To Scale!
To calculate a 3D position (X, Y, Z),
GPS receiver must track at least 4 SV!
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20. Where are you?
Simplified Example:
You are somewhere inside
the blue circle.
You know you are
distance A from
point 1, and
distance B from point 2.
Position calculated by trilateration
A
B
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21. Solution:
Draw a circle around point 1 of radius A
Draw a circle around point 2
of radius B. Find the place
where the yellow and red
circles intersect.
Where are you?
(Remember: you are inside the blue circle)
Trilateration Example
A
B
You are here
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22. GPS & Trilateration
A GPS receiver uses the principle of
trilateration to calculate its position.
In GPS this is really three
dimensional problem, but
that just makes things a
little more complex to solve,
and we will leave the actual
computation to a computer anyway.
Notice: The more accurately a GPS receiver can measure the distance from
itself to a GPS satellite the more accurately it can determine its position !
B
A
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23. Summary of GPS, Trilateration & Accuracy
 GPS accuracy is dependent upon the ability of
the GPS receiver to calculate the distance
between satellites and itself
 More accurate GPS technology requires a
more precise measurement of the distance
between each GPS SV and the GPS receiver
 The more accurately a GPS receiver measures
the distances, the more accurate the calculated
positions (calculated X, Y, Z)

24. LEVELS OF SERVICES
u 1. STANDARD POSITIONING SERVICE
SPS
u 2. PRECISE POSITIONING SERVICE
PPS

25. GOOGLE EARTH

26. GOOGLE EARTH

27. ZOOM
EFFECT

28. What contributes to error in
GPS positions?
 Ionospheric / Tropospheric conditions
 Measurement noise
 Ephemeris Data
 Satellite Clock Drift
 Multipath interference
 Selective Ability (SA)

29. THANK YOU