GH AIS Message Format
NMEA Message Formats
The NMEA message formats are specified in /IEC 61162-1/ these are encoded/decoded using the AIS codec.
NMEA messages originate from transponders (information from ships) or from users (sending AtoN e.g.).
Internal Message Formats
Internal message formats are modelled after the NMEA message formats (see /IEC 61162-1/). Internal messages originate from within the AIS system, basically all other messages than those received by ships or users are encapsulated in the internal message formats.
Two different internal formats are specified in the following, as well as the date format used for the internal messages.
Date format
The date format will be in UTC time and are specified as follows:
Date format=<year>,<month>,<day>,<hour>,<minut>,<second>,<millisecond>
Example=2004,12,31,23,59,59,999
GH Internal Message Type 1
GH internal message type 1 are used for “encapsulating” NMEA messages. The “encapsulation” basically takes places by sending a GH specific message before sending the NMEA message. This has the advantage that GIS systems still should be able to handle the message stream since the unknown GH message should be ignored and the NMEA message interpreted is usual.
The internal message type 1 are specified as follows:
$PGH1,<date format>,<country>,<region>,<pss>,<online data>*hh<CR><LF>
<NMEA message>
- <date format> as specified above
- <country> are the country that the message originates from (HELCOM).
- <region> the MMSI number of the region
- <pss> the MMSI number of the site transponder
- <online data> buffered data from a BSC will be designated with 0. Online data with 1.
- <*hh> checksum as described in /IEC 61162-1/
example: $PGH1,2004,12,21,24,59,59,999,XYZ,219000001,219000002,1*BE<CR><LF>
!BSVDM,1,1,,B,13ANcF00000f1c8Pa8uSB1md00RB,0*6D<CR><LF>