Introduction to GNSS

1. SATELLITE NAVIGATION
GOM 223
IFFAT ARA

2. SATNAV SYSTEM

3. SATNAV SYSTEM

4. SATNAV SYSTEM
• A satellite navigation or satnav system is a system
that uses satellites to provide autonomous geo-
spatial positioning.
• It allows small electronic receivers to determine their
location (longitude, latitude, and altitude/elevation)
to high precision (within a few metres) using time
signals transmitted along a line of sight by radio from
satellites.

5. Time Signal
A time signal is a visible, audible,
mechanical, or electronic signal used as a
reference to determine the time of day.

6. Line-of-sight propagation

7. Line-of-sight propagation
Line-of-sight propagation is a characteristic of
electromagnetic radiation or acoustic wave
propagation which means waves which travel
in a direct path from the source to the receiver.

8. GNSS

9. GNSS
A satellite navigation system with global
coverage may be termed a global
navigation satellite system (GNSS).

10. GNSS & RNSS: Present

11. GPS

12. GLONASS

13. Galileo (in development)

14. Compass (in development)

15. QZSS

16. BeiDou (BDS)

17. IRNSS

18. Global Navigation Satellite Systems
GLONASS
GPS
GALILEO

19. IRNSS
COMPASS
QZSS
Regional Navigation Satellite
Systems

20. Humans have always been Interested
in knowing where Things are………..

21. Where to go ?

22. • Marking trails with piles of stones
(problems when snow falls…or on ocean)
• Navigating by stars
(requires clear nights and careful measurements)
Modern Ideas:
• RADAR
• GNSS
Early Solutions:

23. GLOBAL
POSITIONING
SYSTEM (GPS)
USA

24. • Developed by US Department of Defense
• 1969-Defense Navigation Satellite System (DNSS) formed
• 1973-NAVSTAR Global Positioning System developed
• 1978-first 4 satellites launched
History of the GPS

25. • 1993-24th satellite launched; initial operational
capability
• 1995-full operational capability
• May 2000-Military accuracy available to all users
History of the GPS

26. What is GPS and how it works?
GPS, which stands for Global
Positioning System, is the
system today able to show
you your exact position on
the Earth anytime, in any
weather, anywhere.

27. Satellites
There are quite a number
of satellites out there in
space. They are used for
a wide range of purposes:
satellite TV, cellular
phones, military
purposes and etc.
Satellites can also be
used by GPS receivers.

28. GPS Satellites
The GPS Operational
Constellation consists of
24 satellites that orbit
the Earth in very precise
orbits twice a day. GPS
satellites emit
continuous navigation
signals.

29. Velocity x Time = Distance
*Distance between satellite and
receiver
T
Signal leaves satellite at
time “T”
Distance =Velocity xTime

30. GPS determines locations on Earth

31. Triangulation
Geometric Principle:
You can find one
location if you know its
distance from other,
already-known
locations.

32. Triangulation
Distance measurements from
two satellites limits our
location to the intersection of
two spheres, which is a
circle.

33. Triangulation
A third measurement
narrows our location to
just two points.

34. Since satellite
clocks time is
variable a fourth
measurement
determines
which point is
our true location
Triangulation

35. GPS is based on satellite ranging, i.e. distance from satellites
…satellites are precise reference points
…we determine our distance from them
we will assume for now that we know exactly where satellite is
and how far away from it we are…
if we are lost and we know
that we are 11,000 miles
from satellite A…
we are somewhere on a sphere
whose middle is satellite A
and diameter is 11,000 miles

36. Control Segment
1 Master Station
5 Monitoring Stations
Space Segment
NAVSTAR : Navigation
Satellite Time and Ranging
24 Satellites
20200 Km
User Segment
Receive Satellite Signal
GPS SEGMENTS

37. Space Segment
• 24 Satellites
– 4 satellites in 6 Orbital Planes
inclined at 55 Degrees
• 20,200 Km above the Earth
• 12 Hourly orbits
– In view for 4-5 hours
• Designed to last 7.5 years

38. Period 12 sidereal hours
(~11 hours 58 minutes)
nearly circular
orbit with a semi-
major axis of
26 578 km

39. Control Segment
• Master Control Station
– Responsible for collecting tracking data from the monitoring stations
and calculating satellite orbits and clock parameters
• 5 Monitoring Stations
– Responsible for measuring pseudorange data. This orbital tracking
network is used to determine the broadcast ephemeris and satellite
clock modeling
– Ground Control Stations
– Responsible for upload of information to the satellites

40. C O N T R O L S E G M E N T
1 Master Station 5 Monitoring Stations

41. User Segment
• The most visible segment
• GPS receivers are found in many locations and applications

42. Applications of GPS
• Navigation
• Target tracking
• Search and Rescue
MILITARY

43. Applications of GPS
• GPS for surveying
• Mapping
• Finding lost vehicles
CIVILIAN Purposes

44. • In Europe quota system Fishermen
only allowed to catch certain amount
of a particular species of fish on a
particular fishing ground
• Trials of monitoring fleet
incorporating GPS data
Applications: Monitoring of Fishing Fleet

45. CLASSIFICATION

46. CLASSIFICATION
• GNSS-1
• GNSS-2
• Core Satellite navigation systems
• Global Satellite Based Augmentation Systems

47. CLASSIFICATION
• Regional SBAS
• Regional Satellite Navigation Systems
• Continental scale Ground Based Augmentation
Systems (GBAS)
• Regional scale GBAS
• Local GBAS

48. GNSS - 1

49. GNSS - 1
• GNSS-1 is the first generation system and is the combination of
existing satellite navigation systems (GPS and GLONASS),
with Satellite Based Augmentation Systems (SBAS) or Ground
Based Augmentation Systems (GBAS).
• In the United States, the satellite based component is the Wide
Area Augmentation System (WAAS), in Europe it is
the European Geostationary Navigation Overlay
Service(EGNOS), and in Japan it is the Multi-Functional Satellite
Augmentation System (MSAS). Ground based augmentation is
provided by systems like the Local Area Augmentation
System (LAAS).

50. GNSS - 2

51. GNSS - 2
• It is the second generation of systems that independently
provides a full civilian satellite navigation system, exemplified
by the European Galileo positioning system.
• These systems will provide the accuracy and integrity
monitoring necessary for civil navigation; including aircraft.
• This system consists of L1 and L2 frequencies (in the L band of
the radio spectrum) for civil use and L5 for system integrity.
• Development is also in progress to provide GPS with civil use
L2 and L5 frequencies, making it a GNSS-2 system.

52. CORE SATELLITE
NAVIGATION SYSTEMS

53. Core Satellite navigation systems
• Using a core satellite systems allow for autonomous geo-spatial
positioning with global coverage without any other information.
• GPS: Global Positioning System of the US DoD, operational
• GLONASS: Global Navigation Satellite System of Russia,
operational
• GALILEO: Navigation Satellite System of Europe, in
development
• COMPASS/BeiDou: Global Navigation Satellite System of
China, in development.

54. SATELLITE BASED
AUGMENTATION SYSTEM

55. GSBAS
• The performance of Global Navigation Satellite
Systems (GNSSs) can be improved by regional Satellite-
based Augmentation Systems (SBASs).
• SBAS improves the accuracy and reliability of GNSS
information by correcting signal measurement errors
and by providing information about the accuracy,
integrity, continuity and availability of its signals.

56. GSBAS
• SBAS uses GNSS measurements taken by accurately located
reference stations deployed across an entire continent. All
measured GNSS errors are transferred to a central computing
centre, where differential corrections and integrity messages are
calculated.
• These calculations are then broadcast over the covered area
using geostationary satellites that serve as an augmentation, or
overlay, to the original GNSS message.

57. Existing SBAS

58. Existing SBAS
• USA: Wide Area Augmentation System (WAAS)
• Japan: Multi-functional Satellite Augmentation System (MSAS)
• India: GPS and GEO Augmented Navigation (GAGAN)
• China: Satellite Navigation Augmentation System (SNAS) (in
development)
• South Korea: Wide Area Differential Global Positioning System
(WADGPS) (in development)
• Russia: System for Differential Corrections and Monitoring (SDCM)
(in development).