Installation Manual

38 Issue 1 AIS Installation Manual
7.4.23 VBW – Dual ground/water speed
S—VBW,x.x,x.x,A,x.x,x.x,A,x.x,A,x.x,A*hh<CR><LF>
Status: stern ground speed
Stern traverse ground speed
Status: stern water speed
Stern traverse water speed
Status: ground speed
Traverse ground speed
Longitudinal ground speed
Status: water speed
Traverse water speed
Longitudinal water speed
Longitudinal ground speed – used
Transverse ground speed – used
Status of ground speed - used
Other fields ignored
7.4.24 VDM – VHF data link message
This sentence is output by the transponder each time it receives an incoming message over the
VHF data link. The VDM sentence encapsulates a part of an M.1371 message, and several
VDM sentences may need to be decoded and re-assembled in order to re-construct the original
M.1371 message.
!--VDM,x,x,x,a,s—s,x*hh<CR><LF>
number of fill-bits
encapsulated ITU-R M.1371 radio message
AIS Channel
sequential message identifier
sentence number
total number of sentences needed to transfer message
7.4.25 VDO - AIS VHF Data-link own-vessel report
This sentence is output to all the presentation ports at regular intervals and contains the
contents of the transponders own-vessel report.
Each time the transponder transmits an own-vessel report, it encapsulates the M.1371 message
in one or more VDO sentences and outputs them on its presentation ports.
!--VDO,x,x,x,a,s—s,x*hh<CR><LF>
number of fill-bits
encapsulated ITU-R M.1371 radio message
AIS Channel (‘A’ or ‘B’)
sequential message identifier
sentence number
total number of sentences needed to transfer message
The transponder outputs one VDO sentence every second in addition to echoing all transmitted
VDO sentences as they are transmitted in order to provide frequent updates to all connected
presentation devices. VDO sentences which have also been transmitted contain the appropriate
AIS channel indicator whereas VDO sentences that have not been transmitted contain a NULL
field for the channel indicator.