Satellite Navigation

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 Regiona l 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 x Time

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. CONTROL SEGMENT 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).