Download m12gps

EE587
Spring – 2003
M12 - GPS
Presented by,
Kishore Mogatadakala
02/04/03.
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GPS and the satellite constellation
Principle - segments and operation
GPS equations and different coordinate systems
GPS applications
M12 GPS on-core
M12 technical characteristics
NMEA protocol
Different Global positioning systems
References
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.
GPS Segments
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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
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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
GPS Operation
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 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
ECEF and Geodetic Coordinates
GPS Applications
M12 – On-core receiver
NMEA Protocol
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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
http://yona_n.tripod.com/gps/gps-survey.html#top
Different GPS Modules
Company
Product
Garmin
Diagram
Dimension(mm)
Weight(gm)
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
Company
Product
EMTAC
GPSPCMCIA
Receiver Card
Picture
Dimensions(mm)
Weight(gms)
Type - II
N/A
Compatible With
most of
PDA/Notebook !
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
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