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EE587 Spring – 2003 M12 - GPS Presented by, Kishore Mogatadakala 02/04/03. 1) GPS and the satelli

EE587 Spring – 2003 M12 - GPS Presented by, Kishore Mogatadakala 02/04/03. 1) GPS and the satellite constellation 2) Principle - segments and operation 3) GPS equations and different coordinate systems 4) GPS applications 5) M12 GPS on-core

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EE587 Spring – 2003 M12 - GPS Presented by, Kishore Mogatadakala 02/04/03. 1) GPS and the satelli

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  1. EE587 Spring – 2003 M12 - GPS Presented by, Kishore Mogatadakala 02/04/03. 1) GPS and the satellite constellation 2) Principle - segments and operation 3) GPS equations and different coordinate systems 4) GPS applications 5) M12 GPS on-core 7) M12 technical characteristics 8) NMEA protocol • Different Global positioning systems • References

  2. GPS and Satellite constellation • GPS (Global Positioning System)is a remarkable navigation technology that provides precise time and location. GPS provides the exact time and location anywhere, anytime, and under any atmospheric conditions. • GPS is the acronym for NAVSTAR(Navigation Satellite Timing And Ranging) Global Positioning System. NAVSTAR is the name given to GPS satellites. • GPS is funded by and controlled by the U. S. Department of Defense (DOD). While there are many thousands of civil users of GPS world-wide, the system was designed for and is operated by the U. S. military.

  3. GPS Segments * Space segment GPS Space Segment consists of at least four equally-spaced GPS satellites in a constellation of six orbiting planes at an altitude of 20, 200km. GPS satellites orbit at a 55 degree inclination to the equatorial plane * Control segment To launch and arrange GPS satellites properly in space to provide an optimal GPS system for safety applications. to handle unexpected accidents and to provide exact information in different situations. * User segment GPS User Segment consists of antenna for receiving satellite signals, a GPS receiver for collecting navigation data and for calculating time and location, and other specialized equipment for special purposes

  4. GPS Operation

  5. GPS Equations • where • c = speed of light (3 ´ 108m/s) • tt,1, tt,2, tt,3, tt,4= times that GPS satellites 1, 2, 3, and 4, respectively, transmitted their signals (these times are provided to the receiver as part of the information that is transmitted). • tr,1, tr,2, tr,3, tr,4= times that the signals from GPS satellites 1, 2, 3, and 4, respectively, are received (according to the inaccurate GPS receiver’s clock) • x1, y1, z1 = coordinates of GPS satellite 1 (these coordinates are provided to the receiver as part of the information that is transmitted); similar meaning for x2, y2, z2, etc

  6. ECEF and Geodetic Coordinates

  7. GPS Applications

  8. M12 – On-core receiver

  9. NMEA Protocol • The NMEA 0183 v2.0 protocol is implemented by most GPS equipment, but is in fact a general purpose standard used in marine electronics for navigation and other functions • NMEA 0180 & 0182 recommend that the talker output can be either RS-232 (polar) or TTL (0/5V). NMEA 0183 retains this but recommends RS-422 in addition. (M12-TTL) • The NMEA 0183 protocol supports serial communications at 4800 bps (fixed) using printable ASCII characters only • The data is presented as "sentences” . • Each sentence starts with a "$" character followed by a two-character talker ID followed by a three-character sentence ID followed by data content (a series of comma delimited fields ) The checksum comprises a field starting with a "*" character and two hexadecimal digits (expressed in ASCII) representing the exclusive OR of all characters appearing between the "$" and "*" exclusively Each sentence can have up to 82 characters including the header, the data and an optional checksum field at the end. If a field is blank, all the comma delimiters remain but no data appears between commas corresponding to the blank field. Sentence GGA Function: Global Positioning Fix DataExample:$GPGGA,120757,5152.985,N,00205.733,W,1,06,2.5,121.9,M,49.4,M,,*52Synopsis: time of fix (hhmmss), latitude, N/S, longitude, E/W, Fix quality (0=invalid, 1=GPS fix, 2=DGPS fix), number of satellites being tracked, horizontal dilution of position, altitude above sea level, M (meters), height of geoid (mean sea level) above WGS84 ellipsoid, time in seconds since last DGPS update, DGPS station ID number, checksum

  10. Company Product Diagram Dimension(mm) Weight(gm) Garmin GPS 25 Series gps engine 46.5x70x11.4 38 Motorola M12 Oncore GPS Receiver 40x60x10 25 Trimble Lassen SK-II gps module 83x31x10.2 19.6 U-box TIM gps module (SiRF based) 25x25x3 3 http://yona_n.tripod.com/gps/gps-survey.html#topDifferent GPS Modules

  11. Company Product Picture Dimensions(mm) Weight(gms) EMTAC GPSPCMCIA Receiver CardCompatible With most of PDA/Notebook ! Type - II N/A Teletype GPS GPS WorldNavigator PCMCIA GPS Receiver Type – II 30 Agis Pte Ltd CF Type I 103x48x23 60 EMTAC D157N CF Type - I N/A

  12. References * List of companies and their products ( Including dimensions and weights) http://yona_n.tripod.com/gps/gps-survey.html#top * NMEA 0183 Protocol http://www.scnt01426.pwp.blueyonder.co.uk/Articles/GPS/NMEA.htm * GPS Fundamentals http://www.navicom.co.kr/english/gps/fundamental.asp * M-12 On-core and characteristics http://www.motorola.com/ies/GPS/download/gpsusersguide/gpsusersguidev5chap3.pdf

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