EE587Spring 2003

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 (3 108 m/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
  receivers 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
(No Transcript)
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 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
  (0invalid, 1GPS fix, 2DGPS 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.htmltopD
ifferent GPS Modules
 
 
12
(No Transcript)
13
References

• List of companies and their products (
  Including dimensions and weights)
• http//yona_n.tripod.com/gps/gps-survey.htmltop
• NMEA 0183 Protocol
• http//www.scnt01426.pwp.blueyonder.co.uk/Article
  s/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/gpsusers
  guide/gpsusersguidev5chap3.pdf