The GPS system uses a constellation of satellites that orbit the Earth and transmit precise time and location data. GPS receivers triangulate their position by calculating the distance to multiple satellites using the travel time of signals. The US government maintains GPS for civilian and military use worldwide. Key applications include navigation for vehicles, ships and aircraft as well as uses in mapping, agriculture, recreation and more. The system provides location and timing data to users with an accuracy as precise as a few meters or centimeters depending on the receiver.

1. Global Positioning System
BY DHIREN PARYANI
0206CS111026

2. What is the GPS?
 Orbiting navigational satellites
 Transmit
position and time data
 Handheld receivers calculate
 latitude
 longitude
 altitude
 velocity
 It is maintained by the US government and is
freely accessible to anyone with a GPS receiver

3. History of the GPS
 1969—Defense Navigation Satellite System (DNSS)
formed
 1973—NAVSTAR Global Positioning System
developed
 1978—first 4 satellites launched
Delta rocket launch

4. History of the GPS
 1993—24th satellite
launched; initial
operational capability
 1995—full operational
capability
 May 2000—Military
accuracy available to
all users

5. How does GPS work?
 Measuring distance by measuring time
Satellites send coded signals indicating their position in
space and the exact time the signals are being sent
 Receivers use the time it takes signal to travel from
satellite to receiver to determine distance from satellite to
receiver
 Information from multiple satellites is used to determine
position through ‘triangulation’


6. Three Segments of the GPS
Space
Segment
User
Segment
Control
Segment
Ground
Antennas
Master Station
Monitor Stations

7. Control Segment
US Space
Command
Hawa
ii
Cape
Canaveral
Kwajalein
Atoll
Ascension
Is.
Master Control Station
Diego
Garcia
Monitor Station
Ground Antenna

8. Space Segment

9. 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.


10. GPS Communication and Control

11. GPS receivers
 A GPS receiver's job is to locate four
or more satellites, figure out the
distance to each, and use this
information to deduce its own
location.



Hand-held receivers for recreational use
with accuracy of 10-15 meters
Vehicle mounted receivers for navigation
or agricultural use with accuracy of < 1
meter
Backpack or tripod mounted receivers for
surveying use with accuracy of 5 – 10
centimeters

12. More about GPS receivers
 Receivers require clear line-of-sight; thus, they will
not work indoors or where tall objects obscure the
sky

13. Errors
 Troposphere causes delays in code and carrier
But they aren’t frequency dependent
But the errors are successfully modeled
 Errors due to Multipath
 Receiver noise

14. Errors
 Forces on the GPS satellite
 Earth is not a perfect sphere and hence uneven
gravitational potential distribution
 Other heavenly bodies attract the satellite, but these are
very well modeled
 Not a perfect vacuum hence drag but it is negligible at
GPS orbits
 Solar radiation effects which depends on the surface
reflectivity, luminosity of the sun, distance of to the sun.
this error is the largest unknown errors source

15. DGPS
 Errors in one position
are similar to a local
area
 High performance GPS
receiver at a known
location.
 Computes errors in the
satellite info
 Transmit this info in
RTCM-SC 104 format to
the remote GPS

16. Application of GPS Technology
 Location - determining a basic position
 Navigation - getting from one location to another
 Tracking - monitoring the movement of people and
things
 Mapping - creating maps of the world
 Timing - bringing precise timing to the world

17. Application of GPS Technology
 Private and recreation
 Traveling by car
 Hiking, climbing, biking
 Vehicle control
 Mapping, survey, geology
 English Channel Tunnel
 Agriculture
 Aviation
 General and commercial
 Spacecraft
 Maritime

18. Screen Capture of a GPS enabled phone

19. GPS Navigation

20. Any Queries?

21. Thank You!!