The document discusses the Global Positioning System (GPS). It provides details on: - GPS was developed by the US Department of Defense and uses 27 satellites for positioning. - It is free, precise, reliable, works in all weather, and has unlimited user capacity. - Common applications include vehicle navigation, asset tracking, mapping, and precision agriculture. - GPS determines location by measuring the time it takes for signals from multiple satellites to reach a receiver.

1. PADMASRI DR. B.V.RAJU INSTITUTE OF
COMPUTER EDUCATION
Global Positioning System

2. INTRODUCTION
•
•
•
•
•
•
Developed and maintained by the US Department of Defense
(DOD)
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
Now available in many cars as an option
Created and operated by the
US Department of Defense

3. Three Parts
 Space segment
 Control segment
 User segment
3

4. Characteristics of GPS
• Free
• Precise
Almost!
• Reliable
• All weather
• Anytime & anywhere
• Unlimited user capacity

5. 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

6. GPS IN-VEHICLE NAVIGATION & AGRICUTURE :

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

9. GPS Receivers

10. Methods of data collection
Three methods of positioning
• Autonomous
10-20 meters
• Differential
2-5 meters
• Phase Differential
centimeter
10-20 m
2-5m
cm

11. WAAS
• Wide Area Augmentation System.
• It provides FREE GPS differential correction data for
visible satellites
• Developed & operated by the FAA (Federal Aviation
Administration) for flight navigation but it’s available
free to GPS users
• WAAS-enabled receivers can provide sub-meter level
accuracy anywhere in most locations of the US and
southern Canada.

12. Common use of GPS
A. GIS data collection & mapping
B. Navigation
C. Recreation

13. GPS for Navigation
• GPS in PDA
• Are getting popular in car
• Comes with voice guidance

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

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