3. Contents
• Introduction
• What is GPS
• Types of GPS
• Fundamentals
• Functional segments of GPS
• Advantages and disadvantages of GPS
• Users / application of GPS
• GPS receivers
• Error sources and analysis
• Reference
4. introduction
• navigations system are :-
• Russian equivalent (GLONASS)
• the European equivalent (GALILEO)
• the Chinese equivalent (BeiDou-2)
• Indian Regional Navigation Satellite System ( IRNSS )
• The Quasi-Zenith Satellite System (QZSS) Japanese
• The Global Positioning System (GPS)
5. What is GPS ?
• It’s a technique by which the location of any object , its velocity ,
direction and time can be known precisely at any time whether the
object is on the ground or on the sea surface or in the air
• GPS is invented by the united state department of defense
• Its actual name is NAVTAR ( navigation system with time and ranging)
• The GPS system consists of 24 satellites ( now 32 ) placed in near
circular orbits arrange in 6 orbital planes
6. • The period of revolution is 12 hours , so that at least 4 satellites are available for observation
• GPS is the only system today that can show exact position anytime
GPS answer five questions simultaneously
1. Where am I ??
2. Where am I going ??
3. Where are you ??
4. What are the best way to reach there ??
5. When will I reach there ??
7.
8. Types of GPS
• There are the basic type of survey grade in GPS :-
Single frequency :
its also called static mode
Dual frequency :
its only required post processing when operating in static or
fast static
9. Fundamentals
• The GPS concept is based on time and the known position of
specialized satellites.
• The satellites carry very stable atomic clocks that are synchronized to
each other and to ground clocks.
• Any drift from true time maintained on the ground is corrected daily.
• Likewise, the satellite locations are known with great precision.
• GPS receivers have clocks as well; however, they are not synchronized
with true time, and are less stable.
10. • GPS satellites continuously transmit their current time and position.
• A GPS receiver monitors multiple satellites and solves equations to
determine the exact position of the receiver and its deviation from
true time.
• At a minimum, four satellites must be in view of the receiver for it to
compute four unknown quantities (three position coordinates and
clock deviation from satellite time).
11.
12. Functional segments of GPS
• The GPS is comprised of three segments
1. Space segment
2. Control segment
3. User segment
13. Space segment
• The GPS system consists of 24 satellites ( now 32 ) placed in near
circular orbits arrange in 6 orbital planes
• At 55 degree inclination to equator (tilt relative to the
Earth's equator)
• At 20200 km height and 26600 km orbital radius
• The period of revolution is 12 hours , so that at least 4 satellites are
available for observation
• These 24 satellites form the space segment of GPS
14. Control segment
• The control segment on the ground tracks and maintains the satellites
in the space
The control segment is composed of:
• a master control station (MCS)
• an alternate master control station
• four dedicated ground antennas
• six dedicated monitor stations.
15. • The flight paths of the satellites are tracked by dedicated U.S. Air
Force monitoring stations in :
• Hawaii, Kwajalein Atoll, Ascension Island, Diego Garcia, Colorado
Springs and Cape Canaveral
along the monitor stations operated by National Geospatial-
intelligence ( NGA )
• The tracking information is sent to the Air Force Space Command
MCS at Schriever Air Force Base in Colorado Springs
16. • which is operated by the ( 2d )Space Operations Squadron (2 SOPS)
of the U.S. Air Force
• Then (2 SOPS) contacts each GPS satellite regularly with a
navigational update using antennas
• These updates synchronize the atomic clocks on board the satellites
to within a few nanoseconds of each other, and adjust the
ephemeris of each satellite's internal orbital mode
17. • The updates are created by a Kalman filter that uses inputs from the
ground monitoring stations, space weather information, and various
other inputs
18. User segment
• The user segment is composed of hundreds of thousands of U.S. and
allied military users of the secure GPS Precise Positioning Service
• it tens of millions of civil, commercial and scientific users of the
Standard Positioning Service
• In general, GPS receivers are composed of an antenna, tuned to the
frequencies transmitted by the satellites, receiver-processors, and a
highly stable clock
19. • They may also include a display for providing location and speed
information to the user.
• A receiver is often described by its number of channels:
this signifies how many satellites it can monitor simultaneously.
Originally limited to four or five, this has progressively increased over
the years so that, as of 2007, receivers typically have between 12 and
20 channels.
20.
21. Advantages and disadvantages of GPS
• Advantages :
GPS is extremely easy to navigate as it tells you to the direction for
each turns you take or you have to take to reach to your destination.
GPS works in all weather so you need not to worry of the climate as
in other navigating devices.
The GPS costs you very low in comparison other navigation systems.
22. The most attractive feature of this system is its 100% coverage on the
planet.
It also helps you to search the nearby restaurants, hotels and gas
stations and is very useful for a new place.
Due to its low cost, it is very easy to integrate into other technologies
like cell phone.
23. The system is updated regularly by the US government and hence is
very advance.
This is the best navigating system in water as in larger water bodies
we are often misled due to lack of proper directions
Manpower requirement is very less
24. disadvantages
• Sometimes the GPS may fail due to certain reasons and in that case
you need to carry a backup map and directions.
• If you are using GPS on a battery operated device, there may be a
battery failure and you may need a external power supply which is
not always possible.
• Sometimes the GPS signals are not accurate due to some obstacles to
the signals such as buildings, trees and sometimes by extreme
atmospheric conditions such as geomagnetic storms.
25. Users / application of GPS
The applications of the Global Positioning System fall into five
categories:
location
navigation
timing,
mapping
tracking.
Each category contains uses for the military,
industry, transportation, recreation and science.
26. Each category contains uses for the
1. military
2. industry
3. transportation
4. recreation
5. science
27. Location
• This category is for position determination and is the most obvious
use of the Global Positioning System.
• GPS is the first system that can give accurate and precise
measurements anytime, anywhere and under any weather
conditions.
28. Some example of applications within this category are:
1. Measuring the movement of volcanoes and glaciers.
2. Measuring the growth of mountains
3. Measuring the location of icebergs - this is very valuable to ship
captains helping them to avoid possible disasters.
29. • Storing the location of where you were - most GPS receivers on
the market will allow you to record a certain location .
• This allows you to find it again with minimal effort and would
prove useful in a hard to navigate place such as a dense forest.
30.
31. Navigation
Navigation is the process of getting from one location to another.
This was the what the Global Positioning System was designed for.
The GPS system allows us to navigate on water, air, or land.
It allows planes to land in the middle of mountains and helps
medical evacuation helicopters save precious time by taking the best
route.
32.
33. Timing
• GPS brings precise timing to the us all.
• Each satellite is equipped with an extremely precise atomic clock.
• This is why we can all synchronize our watches so well and make sure
international events are actually happening at the same time
34. Mapping
• This is used for creating maps by recording a series of locations.
• The best example is surveying where the DGPS technique is applied
but with a twist.
• Instead of making error corrections in real time, both the stationary
and moving receivers calculate their positions using the satellite
signals.
35. • When the roving receiver is through making measurements, it then
takes them back to the ground station which has already calculated
the errors for each moment in time.
•
• At this time, the accurate measurements are obtained
36.
37. Tracking
• The applications in this category are ways of monitoring people and things such
as packages.
• This has been used along with wireless communications to keep track of some
criminals.
• The suspect agrees to keep a GPS receiver and transmitting device with him at all
times.
• If he goes where he's not allowed to, the authorities will be notified. This can also
be used to track animals.
38.
39. GPS receivers
• In general, GPS receivers are composed of an antenna, tuned to the
frequencies transmitted by the satellites, receiver-processors, and a
highly stable clock
• They may also include a display for providing location and speed
information to the user.
• A receiver is often described by its number of channels:
40. • this signifies how many satellites it can monitor simultaneously.
• Originally limited to four or five, this has progressively increased over
the years so that , receivers typically have 12 channels.
41.
42. • Types of receiver
1. Type 1 :
these receiver contain no screen for display . It is known as
RS. 232 receivers or GPS mice .. This type of receiver can be connected
to computer by means of a cable
It often used for car navigation system with moving map on the
computer screen
43. 2. Type 2 :
these type of receiver contain screen display information
like location , speed , time ……. Here the computer in the GPS
receiver
Its used in aeroplanes and ships
3. Type 3 :
the principle of these receiver is the same as the above ,
but they often use receiver and special antennas for higher accuracy
44. • This type of receivers are used :
1. Agriculture
2. Surveying
3. Military purpose
4. Mapping and GIS
5. Oil and gas
6. Public safety
45. • Type 4 :
its dedicated single purpose GPS system “ used in cars with a
build- in GPS receiver
you can take the system from one vehicle to another without
hassle
you can only use maps of the device manufacture and you
can not upload your own maps
46. • Type 5 :
this type of receiver are in the form of small chips can be fitted
in the car or on the hand of child
these are useful for tacking of car or lost child
sometime these chips also fitted in the body of animals for
their study
47. Error sources and analysis
• GPS error analysis examines error sources in GPS results and the
expected size of those errors.
• GPS makes corrections for receiver clock errors and other effects, but
some residual errors remain uncorrected
Error sources include
1. signal arrival time measurements
2. numerical calculations
3. atmospheric effects
48. 4. ephemeris and clock data
5. multipath signals
6. multipath natural
7. artificial interference
49. Magnitude of residual errors from these sources depends on
geometric dilution of precision
Artificial errors may result from jamming devices and threaten ships
and aircraft or from intentional signal degradation through selective
availability
