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 9) Different Global positioning systems 10) 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 T o 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  10 8 m/s) t t,1, t t,2, t t,3, t t,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). t r,1, t r,2, t r,3, t r,4 = times that the signals from GPS satellites 1, 2, 3, and 4, respectively, are received (according to the inaccurate GPS receiver’s clock) x 1, y 1, z 1 = coordinates of GPS satellite 1 (these coordinates are provided to the receiver as part of the information that is transmitted); similar meaning for x 2, y 2, z 2, etc

6. ECEF and Geodetic Coordinates

7. GPS Applications

8. M12 – On-core receiver

10. 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 Data Example: $GPGGA,120757,5152.985,N,00205.733,W,1,06,2.5,121.9,M,49.4,M,,*52 Synopsis: 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

11. http://yona_n.tripod.com/gps/gps-survey.html#top http://yona_n.tripod.com/gps/gps-survey.html#top Different GPS Modules CompanyProductDiagramDimension(mm)Weight(gm) GarminGPS 25 Series GPS 25 Series gps engine 46.5x70x11.438 MotorolaM12 Oncore M12 Oncore GPS Receiver 40x60x1025 TrimbleLassen SK-II Lassen SK-II gps module 83x31x10.219.6 U-boxTIMTIM gps module (SiRF based) 25x25x33

12. CompanyProductPictureDimensions(mm)Weight(gms) EMTAC GPSPCMCIA Receiver Card Compatible With most of PDA/Notebook ! Type - IIN/A Teletype GPS GPS WorldNavigator GPS WorldNavigator PCMCIA GPS Receiver Type – II30 Agis Pte Ltd CF Type I103x48x2360 EMTACD157ND157N CFType - IN/A

13. 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/gpsusersguide v5chap3.pdf