1. Global
Positioning
System

2. INDEX
• INTRODUCTION
• HISTORY
• STRUCTURE
• APPLICATIONS
• WORKING OF GPS
• BASIC CONCEPTS OF GPS
• SYSTEM SEGMENTATION
• ERROR SOURCES
• ANALYSIS
• THE SIGNAL
• CONCLUSION

3. INTRODUCTION
• GPS is a revolutionary navigation system
– 24 satellites orbiting the earth
– Provide location within metres or less anywhere on
the globe.
– Now available in many cars as an option
– Created and operated by the US Department of
Defense

4. HISTORY
• Constellation of 27 satellites
– (24 active + 3 spare)
• Orbit 12,600 miles above earth
– (10,900 nautical miles)
• Satellites in 12 hour orbit
• First satellite launched in 1978, 24th
became operational
in 1994
• Selective availability was removed in May, 2000
– Handheld receivers are now much more accurate

5. STRUCTURE

6. Applications of GPS
• In-vehicle Navigation (car, boat, airplane)
• Asset Management
• Construction
• Geologic Research & Mining
• Military Navigation and Operations
• Mapping & Surveying
• Precision Agriculture
• Public Health
• Public Safety
• Wireless Communications

7. WORKING OF GPS
• 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’

8. WORKING OF GPS

9. BASIC CONCEPTS OF GPS
• 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 metres
– Vehicle mounted receivers for navigation
or agricultural use with accuracy of < 1
metre
– Backpack or tripod mounted receivers for
surveying use with accuracy of 5 – 10
centimetres

10. BASIC CONCEPTS OF GPS
• Receivers require clear line-of-sight; thus, they will not
work indoors or where tall objects obscure the sky

11. The total GPS configuration is comprised of three distinct
segments
(1) The space segment-Satellites orbiting the Earth
(2) The control segment-Stations positioned on the Earth’s
equator to control the satellites.
(3) The user segment – Anybody that receives and uses the
GPS signal.
SYSTEM SEGMENTATIONSYSTEM SEGMENTATION

12. ERROR SOURCES
• Ionospheric and atmospheric delays
• Satellite and Receiver clock errors
• Dilution of precision
• Multipath
• Blenders

13. ANALYSIS
• Number of visible satellites
• Position dilution of precision
• Satellite elevations
• Multipath
• Distance between space station and rover receivers

14. A GPS Signal contains three different bits of informationA GPS Signal contains three different bits of information
(1).Pseudo random code(1).Pseudo random code
(2).Ephemeris data(2).Ephemeris data
(3).Almanac data(3).Almanac data
THE SIGNALTHE SIGNAL

15. GPS was originally designed for military use at anyGPS was originally designed for military use at any
time, anywhere on the surface of the earth.time, anywhere on the surface of the earth.
The civilians may also use GPS to marine navigation, carThe civilians may also use GPS to marine navigation, car
navigation and surveyingnavigation and surveying..
CON CLUSIONCON CLUSION