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APPENDIX
A
P-5
GNS - GNNS fix data
$--GNS,hhmmss.ss,llll.lll,a,yyyyy.yyy,a,c--c,xx,x.x,x.x,x.x,x.x,x.x*hh<CR><LF>
| | | | | | | | | | | | |
| | | | | | | | | | | | +--- 11
| | | | | | | | | | | +------ 10
| | | | | | | | | | +---------- 9
| | | | | | | | | +-------------- 8
| | | | | | | | +------------------ 7
| | | | | | | +---------------------- 6
| | | | | | +------------------------- 5
| | | | | +------------------------------ 4
| | | +-------+--------------------------------- 3
| +---+--------------------------------------------- 2
+------------------------------------------------------------- 1
1. UTC of position
2. Latitude, N/S
3. Longitude, E/W
4. Mode indicator
5. Total number of satllite in use,00-99
6. HDOP
7. Antenna altitude, metres, re:mean-sea-level(geoid)
8. Geoidal separation
9. Age of differential data
10. Differential reference station ID
11. Checksum
HDM- Heading – magnetic
This sentence is not used in the current version of NMEA and IEC 61162. Some boaters may want the
GPS compass to indicate the magnetic heading when the boat is only fitted with a magnetic compass.
HDG is calculated by adding a geomagnetic variation to HDT.
$--HDM, x.x, M *hh<CR><LF>
Heading, degrees magnetic
HDT - Heading - true
True heading in degrees obtained by processing RF cycle in the GPS carrier frequency.
$--HDT, x.x, T*hh<CR><LF>
Heading, degrees true
THS – True heading and status
Note: This sentence replaces the deprecated sentence HDT.
Actual vessel heading in degrees true produced by any device or system producing true heading. This
sentence includes a “mode indicator” field providing critical safety related information about the heading
data, and replaces the deprecated HDT sentence.