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LA000577C © 2006 Navman New Zealand. All rights reserved. Proprietary information and specications subject to change without notice.
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Unused messages
Input messages where the message ID is not between 100 and 255, or where the message
ID does not correspond to a specied function, result in the response:
$PTTK,INVALID*CS
Errors
Errors in message receipt (other than checksum errors) result in the response:
$PTTK,ERROR,xx*CS
where xx is a hexadecimal error code.
Magnetic Variation (Declination)
The Jupiter 20 module calculates the magnetic variation (the Jupiter 30 does not).
Magnetic Variation elds in $GPRMC
The last two elds in the message $GPRMC are the magnetic variation. An Easterly variation
should be subtracted from, or a Westerly variation added to, the true heading to give the
magnetic heading (the heading given by a magnetic compass).
For example, the output might be:
$GPRMC,220137.250,A,4331.9077,S,17238.2308,E,0.075949,168.82,071004,23.1,E*4C
Standard SiRF output:
$GPRMC,220137.250,A,4331.9077,S,17238.2308,E,0.075949,168.82,071004,,*17
Magnetic Heading eld in $GPVTG
The third eld in the message $GPVTG is the magnetic heading (denoted by the ‘M’ in the
following eld). This is the heading that would be reported by a magnetic compass.
For example, the output might be:
$GPVTG,168.82,T,145.70,M,0.08,N,0.14,K*41
The standard SiRF output:
$GPVTG,168.82,T,,M,0.08,N,0.14,K*58
3.3.3 Altitude output
The module outputs the correct altitude and geoid separation in the $GPGGA NMEA
message. Most SiRFstar-based modules output the height above the current datum (usually
WGS84) ellipsoid as the altitude, contrary to the NMEA specication, and older modules
omit the geoid separation. The Jupiter receiver outputs the height above mean sea level, as
required by the NMEA specication.
For example, the output might be:
$GPGGA,220137.869,4331.9077,S,17238.2308,E,1,06,1.6,61.7,M,11.3,M,0.0,0000*55
Standard SiRF output (v2.3 and earlier):
$GPGGA,220137.869,4331.9077,S,17238.2308,E,1,06,1.6,72.0,M,,M,0.0,0000*6D
Or (v2.3.1 and 2.3.2):
$GPGGA,220137.869,4331.9077,S,17238.2308,E,1,06,1.6,72.0,M,11.3,M,0.0,0000*50