USGlobalsat EM-506 - Manual (Page 12)

EM-506
High Performance GPS Module
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VTG - Course Over Ground and Ground Speed
Note – Fields marked in italic red apply only to NMEA version 2.3 (and later) in this NMEA
message description
Table B-10 contains the values for the following example:
$GPVTG,309.62,T,,M,0.13,N,0.2,K,A*23
Table B-10 VTG Data Format
Name Example Units Description
Message ID $GPVTG VTG protocol header
Course 309.62 degrees Measured heading
Reference T True
Course degrees Measured heading
Reference M Magnetic
1
Speed 0.13 knots Measured horizontal speed
Units N Knots
Speed 0.2 Km/hr Measured horizontal speed
Units K Kilometers per hour
Mode A A=Autonomous, D=DGPS,
E=DR
N=Output Data Not Valid
R= Coarse Position
2
S=Simulator
Checksum *23
<CR><LF> End of message termination
1. SiRF Technology Inc. does not support magnetic declination. All “course over ground” data
are geodetic WGS84 directions.
2. Position was calculated based on one or more of the SVs having their states derived from
almanac parameters, as opposed to ephemerides.