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Technical reference
Page 70
6.8.19 VTG - Course over ground and ground speed
The vessels actual course and speed relative to ground.
6.9 Output data sentence formats
All data output is via IEC61162 / NMEA 0183 sentences. The sentences used by the AIS transceiver are
documented in the subsequent sections. The sentence structure tables describe each field in the sentence
starting from the left most field (field 1) after the sentence identifier. All sentences are terminated with the
IEC61162 checksum shown as ‘*hh’. For details of the checksum calculation please refer to IEC61162-1.
All sentences start with the delimiter “$” or “!” followed by the talker equipment type identifier. The identifier for
AIS is “AI”, e.g., “AIABK”.
6.9.1 ABK - Addressed and binary broadcast acknowledgement
The ABK sentence is generated when a transaction, initiated by reception of an ABM, AIR, or BBM sentence
is completed or terminated.
7 xx
Estimated month of arrival at destination, 00 to 12 (UTC)
8 x.x Navigational status, 0 to 15
9 x.x Regional application flags, 0 to 15
$--VTG, x.x, T, x.x, M, x.x, N, x.x, K,a*hh<CR><LF>
Field
number Description
1 x.x, T Course over ground, degrees true
2 x.x, M Course over ground, degrees magnetic - NOT USED
3 x.x, N Speed over ground, knots
4 x.x, K Speed over ground, km/h
5 a Mode indicator:
A = Autonomous mode
D = Differential mode
E = Estimated (dead reckoning) mode
M = Manual input mode
S = Simulator mode
N = Data not valid
$--ABK,xxxxxxxxx,a,x.x,x,x*hh<CR><LF>
Field
number Description
1 xxxxxxxxx MMSI of the addressed destination AIS transceiver
2 a AIS channel of reception
3 x.x ITU-R M.1371 message ID
4 x Message Sequence Number
5 x Type of acknowledgement
$--VSD,x.x,x.x,x.x,c--c,hhmmss.ss,xx,xx,x.x,x.x*hh<CR><LF>