This document provides an overview and review of the book "Global Positioning System" by Akash Deep Sharma. The 232-page book published in 2008 provides a comprehensive guide to GPS technology, explaining how GPS works, its various components and uses for navigation, recreation, and other applications. It covers topics such as satellite positioning, sources of error, augmented GPS, and future improvements and alternatives to GPS from other countries. The review notes that the book is technically detailed and most suitable for readers interested in developing an understanding of GPS systems and applications.
2. About the Book
• Date Published: 2008
• ISBN: 978-81-7533-106-8
• Length: 232 pages
• Reprint Unavailable
• Availability: Paperback and Hardcover; Available in Indian
Market
• Cost Rs895/-
3. About the Book(contd.)
With insights from knowledge about technologies throughout the
world this comprehensive, step-by-step guide includes strategies to
help you:
•Identify what is GPS by giving its introduction.
•Achieve your related goals by using GPS.
•Make familiarization with GPS and related technology.
•Get acquainted to following terms- GPS tracking, Triangulation,
Differential and augmented GPS, GNSS,
•Access commercial assesment of GPS.
4. About the Book(contd.)
• Access role of GPS in Security related issues.
• Appreciate need of future improvements in GPS and related
technologies.
5. About the Author
• Akash Deep Sharma has obtained MCA from Jaipuria Inst. of
Management Vasundhra(Ghaziabad).
• Has worked for Private, Government as well as semi Govt. Bodies.
• Has made and implemented software for tracking and monitoring of
traffic through GPS system.
• Has been awarded many study projects from private as well as govt
Universities.
• Presently working at Nimble technologies, New Delhi as developer for
web integration and GPS Systems.
6. Theme of the book
• This book is a guide for GPS.
• Numerous technical know-how quoted in relation of related
concepts.
• One of the best topic specific book for GPS.
• Increasing use of GPS has made it much more relevant today.
• Lacks updated things about theory which one could find from
other sources.
8. What is GPS ?
A very precise positioning system
• Developed and maintained by the US
Department of Defense (DOD)
• Satellite Based
* 24 satellites
* 20,200 km high orbit
9. BUT!
Although it is a very precise
geographic positioning system
•It is very easy to get youself into trouble
•Why?
•Because you (probably) don’t understand
how it works
•And that leads to garbage
10. Global Positioning System: An
Introduction
•Fully functional GNSS(=Global Navigation Satellite
System).
•Minimum 24 satellites are required, group known
as constellation.
•Uses microwave signals
•Known as NAVSTAR GPS.
•Developed by US dept. of Def.
•Constellation managed by US AF 50th
Space Wing
11. Global Positioning System: An Introduction
• System has three segments:
1. Space Segment
2. Control Segment
3. User Segment
12. Characteristics of GPS
• Free
• Precise
• Reliable
• Anytime & anywhere
• All weather
• Unlimited user capacity
Almost!
13. Segments of GPS
1. Space Segment
A constellation of 24 satellites
2. Monitor Station
A network of earth-based facilities
3. Users & Equipment
Source:Trimble
16. How GPS Works ………
Uses measurements from 4+ satellites
Distance = travel time x speed of light
Source:Trimble
17. Determining GPS Position
• Suppose the distance from
Satellite A to our position is
11,000 miles
• At this point we could be located
anywhere on the specified sphere
Satellite A
+
• Next, let us take another measurement
from a second satellite, Satellite BSatellite B
+
• Now our position is narrowed down to the
intersection of theses two sphere
18. Satellite C
+
Determining GPS Position
Satellite A
Satellite B
+
+
• Taking another measurement
from a 3rd
satellite narrows our
position down even further, to
the two points
• So by ranging from 3 satellites we can
narrow our position to just two points in space
• These points are located where
the 3rd
sphere cuts through the
the intersection of first two spheres
19. Satellite C
+
How do we decide which one is our
true location?
Satellite A
Satellite B
+
+
• We could make a 4th
measurement
from another satellite to determine
the true point
• However, GPS receivers use a 4th
satellite to precisely
locate our position
• We can eliminate one of the two
points that gives a ridiculous
answer
• The ridiculous point may be too
far from the earth
OR
21. How accurate is GPS?
Depends on some variables
• Design of receiver
• Relative positions of satellites,
technically known as PDOP (Position
dilution of precision)
• Postprocessing
• Time spent on measurement
24. Methods of data collection
Three methods of positioning
• Autonomous
10-20 meters
• Differential
2-5 meters
• Phase Differential
centimeter
2-5m10-20 m
cm
25. How accurate is GPS?
Depends on some variables
• Design of receiver
• Relative positions of satellites,
often known as DOP (Dilution of
Precision)
• Postprocessing
• Time spent on measurement
26. 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.
27. WAAS
• Differential corrections are computed from
ground stations and then uploaded to
geostationary satellites for broadcasting
• WAAS-enabled GPS receiver automatically
uses such correction data to enhance the
positional accuracy
29. Multipath
• When GPS signals arrive at the receiver
having traveled different paths
30. What is a PDOP?
• Position Dilution of Precision
Good PDOP Poor PDOP
31. SNR (signal-to-noise ratio)
• SNR determines the signal strength
relative to noise
• GPS position is degraded if the SNR of
one or more satellites in the
constellation falls below certain range
Signal Strength
Indicators
49. Future Improvements in GPS
• Other nations including India are developing their own Satellite
System for tracking and navigation.
• Includes Glonass from Russia, Galellio from EU and Gagan by ISRO.
•
50. Language of the Book
• Language of the Book is easy and it can be understood easily
however there are technical vocab and jargons which one will need
to refer.
51. Basic Concept
• Basic concept of the book is to give
knowledge about GPS and related
technologies.
• It’s a pure technical book, may prove to
be a boring one if reader lacks technical
aptitude
• A must read for people who come
across such gadgets at daily basis.
52. Conclusion
• This book is mostly meant for those who
want to develop knowledge about GPS
system and related technologies; it not
only teaches application and
appreciation of this technology but also
explains the concept-the physics and
mathematics at work behind this whole
enabling the end user to give a second
hand experience of its working.
Notas do Editor
At the cost of 15 billion dollar of your tax money
At the cost of 15 billion dollar of your tax money
Speed of the light: 186,000 mile/sec
300,000 km/sec
3x10^8 meter/sec
SNR is also known as signal strength
When SA was on, the position could be anywhere on 1st, 2nd, Alpine, or Spruce street. With SA removed, the position is located with in the road width of +/- 15 feet. (road = 35’, the circle is of 20’ radius). Before the location was within 100 meters, that is the point is about a football field away. Now it’s within the 10 meters. Removal of SA made GPS more useful and handy for our day to day use in cell phone, car, watch etc.
Farm equipment capable of producing yield map during harvesting shows how crop yield varies across the field. Allowing farmers to plan fertilizer application for future crops.
