GPS definition

1. 2 GPS concepts By Mahmoud El Mewafi Mmewafi1@ excite.com Professor of Surveying and Geodesy, Public Works Dept., Faculty of Engineering, Mansoura University, Egypt. Tel 002 0127440767

4. GPS (Global Positioning System)

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

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

10. GPS – User Segment (Receivers)

12. Position is Based on Time T + 3 Distance between satellite and receiver = “3 times the speed of light” T Signal leaves satellite at time “T” Signal is picked up by the receiver at time “T + 3”

13. GPS theory

14. XYZT

15. Signal From One Satellite The receiver is somewhere on this sphere.

16. Signals From Two Satellites

17. Signals From Two Satellites X? 5 Sec 3 Sec

18. Three Satellites (2D Positioning)

19. 2D-3 Satellites 5 Sec 3 Sec X 4 Sec

20. Three Dimensional (3D) Positioning

24. Generation of L1 Band Signal

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

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

30. DOP is the Geometric Orientation of Satellites with respect to the Antenna

32. Ideal Satellite Geometry N S W E

33. Good Satellite Geometry

34. Good Satellite Geometry

35. Poor Satellite Geometry N S W E

36. Poor Satellite Geometry

37. Poor Satellite Geometry

38. GPS Navigation: On the Ground Active GOTO Waypoint Location Where GOTO Was Executed Bearing = Course Over Ground (COG) = Cross Track Error (XTE) = Bearing = 65 0 COG = 5 0 XTE = 1/2 mi. Bearing = 78 0 COG = 350 0 XTE = 1/3 mi. Bearing = 40 0 COG = 104 0 XTE = 1/4 mi. Active Leg N

41. Planning a Navigation Route Start = Waypoint

42. How A Receiver Sees Your Route

43. GPS Waypoint Circle of Error X

48. Real Time Differential GPS 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 DGPS Site x +30, y +60 x +5, y -3 x -5, y +3 DGPS Receiver Receiver

49. Differential Correction 2 10m 10m Base Station (w/known coordinates) Receiver (unknown Location) GPS Receiver Estimated Location Differentially Corrected Estimated Position GPS Estimated Location Actual (Known) Position

54. Wide Area Augmentation System Geostationary WAAS satellites GPS Constellation WAAS Control Station (West Coast) Local Area System (LAAS) WAAS Control Station (East Coast)

55. How good is WAAS? With Selective Availability set to zero, and under ideal conditions, a GPS receiver without WAAS can achieve fifteen meter accuracy most of the time.* Under ideal conditions a WAAS equipped GPS receiver can achieve three meter accuracy 95% of the time.* * Precision depends on good satellite geometry, open sky view, and no user induced errors. + - 3 meters +-15 meters

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69. Online Criminal Database

76. Garmin’s cheapest receivers Garmin’s iQue 3600 PDA: http://www.garmin.com/products/iQue3600/ Garmin’s Forerunner 201: A watch that uses GPS to determine current speed, average speed, exact distance traveled, etc. ( ) Basic features also available in the Forerunner 101 ($115). http://www.garmin.com/products/forerunner201/

77. Garmin GPSmap60-C Main Screens Time & Date

78. Garmin GPSmap60-C Satellite Page Location Satellite Strength Accuracy Estimate Skyplot

79. Garmin GPSmap60-C Mark Waypoint Name Symbol Average

80. Garmin GPSmap60-C Main Screens Setup By default, the GPSmap60 will record a Track (line feature) whenever the unit is turned on. Map (GoTo) Profiles

81. Bluetooth GPS Receivers Teletype’s Mini-bluetooth GPS receiver ($175) http://www.mightygps.com/Manufacturer/minibluetooth.htm Teletype’s USB GPS receiver for Laptops ($170) http://www.teletype.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=1250&Category_Code=

82. HP’s Ipaqs and other PDAs with GPS software Hewlett-Packard’s new iPAQ h1945 PDA Now comes equipped with a hp GPS receiver and navigation system ($500) http://www.shopping.hp.com/cgi-bin/hpdirect/shopping/scripts/product_detail/product_detail_view.jsp?BV_SessionID=@@@@0280349227.1102102313@@@@&BV_EngineID=ccckadddfdjlkdgcfngcfkmdflldfgg.0&landing=null&category=handhelds&subcat1=classic_performance&product_code=PF527A%23ABA&catLevel=3 Garmin’s iQue 3600 PDA: http://www.garmin.com/products/iQue3600/

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84. GPS – Ellipsoid - Datum GPS uses the WGS84 (World Geodetic System of 1984) as mathematical surface (model) of the earth Elevations are referenced to Height Above Ellipsoid (HAE)

87. Lat: 40 N Lo: 20 W 60 N 40 N 20 N 20 S 40 S 60 S Equator Prime Meridian 20 W 20 E Lat: 40 00’.00N Lo: 020 00’.00W Lat: 40 00’.00S Lo: 020 00’.00W Every place on earth has a unique location 180 Lo approx. International Date Line o o o O o o o o o o o o o o o

88. 60 04’ .20” N 149 26’.10” W o o 60 o 05’ 149 30’W o 20’

90. By Mahmoud El Mewafi Mmewafi1@ excite.com Professor of surveting and Geodesy, Public Works Dept., Faculty of Engineering, Mansoura University, Egypt 6 Datum Transformations

91. سطوح المقارنة لكل من الكرة الأرضية ونظام الجي بي اس وعملية تحويل القياسات بينهما Sat. 2 Receiver X Z Y (0, 0, 0) WGS-84 Local Sat. 3 Sat. 1 Sat. 4

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