1. Global Positioning System Anurag Mishra Deputy Director Forest Survey of India, Dehradun

2. Outline for Today Today, we will review the basics of the GPS system and Its history Key components Functioning Applications etc.

3. Trying to figure out where you are and where you're going is probably one of man's oldest pastimes

4. Latitude & Longitude 78°01’31.2” E and 30°20’01.6” N 135° 7’45.9” W and 8°37’24.4” S

5. A Little Bit of History In the past, humans had to go to pretty extreme measures to keep from getting lost. They erected monumental landmarks, laboriously drafted detailed maps and learned to read the stars in the night sky. For centuries, only way to navigate was to look at position of sun and stars.

6. Things are much easier today Starting Rs.10,000/- you can get a pocket-sized gadget that will tell you exactly where you are on Earth at any moment. As long as you have a GPS receiver and a clear view of the sky.

7. Why GPS ? Accurate & Precise Efficient, Economical Easy to Operate Portable Navigation Works Everywhere Additional Information

8. Outer Description Internal GPS antenna Battery compartment Display screen External power & data connector Functional keys

9. Primary Pages

10. GPS Information Page Data Fields (speed, elevation and accuracy) Receiver Status Satellite Location(sky view) Satellite signal Strength Date & Time Current Location

11. Satellite Location (Sky View) Satellites numbers becomes highlighted whose data is received and computed. Sky view can be oriented north or your current track towards the top of display.

12. Signal Strength Bar 1.If bar is light gray : GPS accruing the data. 2.When bar turns to black: GPS using the signal for navigation. 3.A “D” in or above the bar: Indicates differential corrections are applied to the satellite.

13. Timeline Feasibility studies begun in 1960s In 1978 the first experimental GPS satellites were launched By December 1993 the GPS system achieved initial operational capability By January 1994 a complete constellation of 24 satellites was in orbit

14. Contd. Full Operational Capability was declared by NAVSTAR in April 1995 The most recent launch was on 17 November 2006 The oldest GPS satellite still in operation was launched in August 1991

15. Background (Cont’d) The essential components of GPS were the 24 Navstar satellites built by Rockwell International, each the size of a large automobile. Each of these 3,000- to 4,000-pound solar-powered satellites circles the globe at about 12,000 miles (19,300 km), making two complete rotations every day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites "visible“ in the sky. Day-to-day running of GPS program and operation of system rests with the Department of Defense (DoD).

16. What is GPS? Satellite-based navigation system Continuously transmits coded information Precisely identify locations Measuring distances from the satellites Man-made stars

17. Introduction Developed by US Department of Defense in 1978 24 Satellites in 6 orbits Situated at an altitude of 20,200 km Life of Satellite is about 7.5 to 10 years 12 hours period and orbit is precisely predictable

18. Contd. Satellite clock: Atomic (Rubidium, Cesium) Powered by solar energy There are no subscription fees or setup charges to use GPS No restriction in using GPS signals Doesn’t work under dense canopy, covered areas GPS works in all weather conditions

19. Global Positioning System (GPS) NAVSTAR NAVigation Satellite Timing And Ranging satellites (NATO) GLONASS GLObal NAvigation Satellite System (Russian) Galileo To be operational by 2012 (EU)

20. NAVSTAR The only fully functional Global Navigational Satellite System Constellation of at least 24 Medium Earth Orbit Satellites that transmit precise Microwave signals, the system enables a GPS Receiver to determine its Location, speed/direction, and time The cost of maintaining the system is approximately US$750 million per year, including the replacement of aging satellites, and research and development

21. NAVSTAR NameLaunch PeriodNumber of Satellites Launched Currently in Service Block I1978-1985110 Block II1985-199090 Block IIA1990-19971915+1 1 Block IIR1997-200412 Block IIR-M2005-33 Total5430+1

22. Global Navigational Satellite System (European) Known as Galileo it is to be built by the European Satellite Navigation Industries for the European Union (EU) and European Space Agency (ESA) as an alternative to the US and the Russian System Galileo is intended to provide: More precise measurements to all users than available through GPS or GLONASS

23. Global Navigational Satellite System (European) Better positioning services at high latitudes, An independent positioning system upon which European nations can rely upon even in times of war or political disagreement. The current project plan has the system as operational by 2011–12, three or four years later than originally anticipated

24. The Open Service (OS) will be free. An accuracy of <4 m horizontally and <8 m vertically if they use both OS bands. A single band will still achieve <15 m horizontally and <35 m vertically, comparable to what the civilian GPS C/A service provides today. The encrypted Commercial Service (CS) will be available for a fee and will offer an accuracy of better than 1 m. The CS can also be complemented by ground stations to bring the accuracy down to less than 10 cm. Global Navigational Satellite System (European)

25. Global Navigation Satellite System (GLONASS) Russian GLONASS (Global'naya Navigatsionnaya Sputnikovaya Sistema) It was developed by the former Soviet Union Now operated for the Russian Government by the Russian Space Forces. Development on the GLONASS began in 1976, with a goal of global coverage by 1991.

26. Global Navigation Satellite System (GLONASS) Beginning in 1982, numerous satellite launches progressed the system forward until the constellation was completed in 1995. Following completion, the system rapidly fell into disrepair with the collapse of the Russian economy. Beginning in 2001, Russia committed to restoring the system, and in recent years has diversified and accelerated the program with a goal of restoring global coverage by 2009.

27. Indian Regional Navigational Satellite System (IRNSS) This is a developmental autonomous regional Satellite Navigation System being constructed and controlled by the Indian Government. It is intended to provide an absolute position accuracy of better than 20 meters throughout India and within a region extending approximately 1,500 to 2,000 km around it. A goal of complete Indian control has been started, with the space segment, ground segment and user receivers all being built in India.

28. Indian Regional Navigational Satellite System (IRNSS) The Government approved the project in May 2006, with the intention to implement within six to seven years. The first satellite of the proposed constellation, developed at a cost of Rupees1,600 crores, is expected to be launched in 2009. The proposed system would consist of a constellation of seven satellites and a support ground segment. The satellites would weigh approximately 1,330 kg and their solar panels generate 1,400 watts of energy.

29. Beidou Navigation System (Chinese) Beidou Satellite Navigation and Positioning System is a project by China to develop an independent Satellite Navigation System. The current Beidou-1 system (made up of 4 satellites) is experimental and has limited coverage and application. However, China has planned to develop a truly global satellite navigation system consisting of 35 satellites (known as Compass or Beidou-2).

30. Beidou Navigation System (Chinese) Beidou 1A was launched on 30 October 2000, Beidou 1B followed 20 December 2000, and Beidou 2A was put into orbit on 24 May 2003.The latest Beidou navigation satellite was successfully launched on 3 February 2007 China joined the Galileo Positioning System project in September 2003 and will invest US$296 million in Galileo over the next few years On November 2, 2006, China announced that from 2008 Beidou would offer open service with an accuracy of 10 meters.

31. GPS CONSTELLATION

32. Orbits of Different Satellites Earth 1000 km 35,768 km 10,000 km LEO (Iridium)GEO (Inmarsat) HEO MEO (ICO) Not drawn to scale

33. Different Roles for Satellites Weather satellites help meteorologists predict the weather or see what's happening at the moment. The satellites generally contain cameras that can return photos of Earth's weather. Communications satellites allow telephone and data conversations to be relayed through the satellite. The most important feature of a communications satellite is the transponder -- a radio that receives a conversation at one frequency and then amplifies it and retransmits it back to Earth on another frequency.

34. Different Satellites (Cont’d) Broadcast satellites broadcast television signals from one point to another (similar to communications satellites). Scientific satellites perform a variety of scientific missions. The Hubble Space Telescope is the most famous scientific satellite, but there are many others looking at everything from sun spots to gamma rays. Navigational satellites help ships and planes navigate, e.g., GPS.

35. Different Satellites (Cont’d) Rescue satellites respond to radio distress signals. Earth observation satellites observe the planet for changes in everything from temperature to forestation to ice-sheet coverage. Military satellites are up there, but much of the actual application information remains secret.

36. What does a GPS receiver do? Position and coordinates. The distance and direction between any two waypoints What direction you are heading Some models can show you: how fast you are going your altitude a map to help you arrive at a destination

37. How does the GPS work? Using satellites in the sky, ground stations on earth, and a GPS receiver, the distances between each of these points can be calculated. The distance is calculated based on the amount of time it takes for a radio signal to travel between these points. This allows the GPS receiver to know where you are, in terms of latitude and longitude, on the earth.

38. Triangulation A GPS receiver's job is to locate four or more of these satellites, figure out the distance to each, and use this information to deduce its own location. This operation is based on a simple mathematical principle called triangulation or trilateration. Triangulation in three-dimensional space can be a little tricky, so we'll start with an explanation of simple two-dimensional trilateration.

39. Triangulation

40. 3D Triangulation Fundamentally, three-dimensional trilateration is not much different from two-dimensional trilateration, but it's a little trickier to visualize. Imagine the radii from the examples in the last section going off in all directions. So instead of a series of circles, you get a series of spheres.

41. GPS Triangulation If you know you are 10000 miles from satellite A in the sky, you could be anywhere on the surface of a huge, imaginary sphere with a 10000-mile radius. Earth 10000 miles

42. GPS Triangulation (Cont’d) If you also know you are 15000 miles from satellite B, you can overlap the first sphere with another, larger sphere. The spheres intersect in a perfect circle. 10000 miles 15000 miles

43. GPS Triangulation (Cont’d) The circle intersection implies that the GPS receiver lies somewhere in a partial ring on the earth. Possible Locations of GPS Receiver Perfect circle formed from locating two satellites

44. GPS Triangulation (Cont’d) If you know the distance to a third satellite, you get a third sphere, which intersects with this circle at two points.

45. GPS Triangulation (Cont’d) The Earth itself can act as a fourth sphere -- only one of the two possible points will actually be on the surface of the planet, so you can eliminate the one in space. Receivers generally look to four or more satellites, however, to improve accuracy and provide precise altitude information.

46. Calculating Distance Distance = Speed x time

47. Control Segment Space Segment User Segment Three Segments of the GPS Monitor Stations Ground Antennas Master Station

48. The Space Segment Arranged in the orbits in such a way that at least 4 satellites are always available Circle earth once every 12 hours Functions Receive and store information from ground control segment Maintain very accurate time Transmit signal to the earth

49. Kwajalein Atoll US Space Command The Control Segment Hawaii Ascension Is. Diego Garcia Cape Canaveral Ground Antenna Master Control Station Monitor Station

50. The User Segment

51. Military. Search and rescue. Disaster relief. Environment, Forestry & Wildlife Marine, aeronautical and terrestrial navigation. Remote controlled vehicle and robot guidance. Satellite positioning and tracking. Shipping. Geographic Information Systems (GIS). Recreation. User Segment

52. GPS Receivers Better units have multiple receivers, so they can pick up signals from several satellites simultaneously. Radio waves travel at the speed of light (about 186,000 miles per second, 300,000 km per second in a vacuum). The receiver can figure out how far the signal has traveled by timing how long it took the signal to arrive.

53. Downloading of GPS Data Data Cable Mapsource Pathfinder

54. Standard Positioning System (SPS) Provided on the GPS L1 frequency. Contains a coarse acquisition (C/A) code and a navigation data message. The P-code and the L2 frequency is not unavailable to SPS users. Accuracy 100 m in horizontal position 156 m in the vertical component

55. Precise Positioning System (PPS) Available to authorized military users and users with PPS receivers This consists of the SPS signal plus the P code on L1 and the carrier phase measurements on L2 Accuracy 22 m in horizontal position 27 m in the vertical component DGPS is used for higher accuracy

56. Differential GPS There is no such thing as a Differential GPS It is the Differential capability Geodetic GPS

57. Differential GPS Uses the point position derived from either the C/A or P- codes Applies correction to that position. These corrections, difference of determined position and the known position, are generated by a reference receiver, whose position is known and is fed to the instrument. Used by the second receiver to correct its internally generated position.

58. DGPS Site x+30, y+60 x+5, y-3 True coordinates = x+0, y+0 Correction = x-5, y+3 DGPS correction = x+(30-5) and y+(60+3) True coordinates = x+25, y+63 x-5, y+3 Real Time Differential GPS DGPS Receiver Receiver

59. Causes of Errors Ionosphere and troposphere delays Signal multipath Orbital errors Number of satellites visible Satellite geometry/shading Intentional degradation of the satellite signal

60. Sources of Signal Interference Earth’s Atmosphere Solid Structures Metal Electro-magnetic Fields

61. Sources of GPS Error F Standard Positioning Service (SPS ): Civilian Users F SourceAmount of Error Satellite clocks:1.5 to 3.6 meters Orbital errors:< 1 meter Ionosphere:5.0 to 7.0 meters Troposphere:0.5 to 0.7 meters Receiver noise:0.3 to 1.5 meters Multipath:0.6 to 1.2 meters Selective Availability User error:Up to a kilometer or more

62. Introduced Errors in GPS Selective Availability To reduce horizontal positioning capabilities from approximately 20 m to 100m Anti Spoofing Encryption of the ‘P-Code’

63. Receiver Errors are Cumulative! User error = +- 1 km System and other flaws = < 9 meters

64. Ideal Satellite Geometry N S W E

65. Good Satellite Geometry

66. Poor Satellite Geometry

67. Planning a Navigation Route Start = Waypoint

68. Applications in Forestry Location of Plantations Area and Perimeter Areas Assessment of TOF Resources

69. Wildlife Management Wildlife Census, Habitats Direct/Indirect sightings Wildlife offenses Settlements

70. Habitations & Encroachments Forest Villages Encroachments Settlements inside forests Delineation of Areas

71. Boundary Pillars Location of Pillars Bearings Distance between pillars Track between the pillars

72. Use of GPS by FSI Ground truthing Forest Inventory Assessment of TOF Monitoring of FDAs

73. Major Suppliers of GPS Garmin Magellan Leica Lawrence NaviGPS

74. GPS Models Garmin E-Trex 12 channels, 500 WP, EC, US$ 119.95 Garmin GPS 12 12 channels, 500 WP, EC, AC, WAAS, US$ 149.95

75. GPS Models Garmin GPS 76 12 channels, 500 WP, EC, AC, WAAS, US$ 219.95 Garmin GPS 76 Map 12 channels, 1000 WP, AC, EC/BM, WAAS, Map, US$ 379.95

76. GPS Models E-Trex Vista 12 channels, 1000 WP, EC, AC, WAAS, US$ 329.95 E-Trex Summit 12 channels, 500 WP, EC, Barometer, Altimeter US$ 219.95

77. GPS Models Magellan Explorist 500 14 channels,8 MB, SD card, 500 WP, EC, AC, WAAS, Map, US$ 329.95 Magellan Explorist 400 14 channels,8 MB, SD card, 500 WP, EC, AC, WAAS, Map, US$ 279.95

78. GPS Models Lawrence iFinder Explorer 12 channels, 500 WP, EC/BM, AC, WAAS, US$ 229.95 Lawrence iFinder H2O 12 channels, 500 WP, EC, AC, WAAS, US$ 169.95

79. Important Battery Life Size & Weight DGPS Capability Price Specifications Requirements