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author | Eric S. Raymond <esr@thyrsus.com> | 2010-12-04 11:53:34 -0500 |
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committer | Eric S. Raymond <esr@thyrsus.com> | 2010-12-04 11:53:34 -0500 |
commit | 238ff98ef02863be9a8a36f6b8005f53301439e2 (patch) | |
tree | 45383d3dc7d33f8b08fbc4dc5b0d7a02dca1b16c /www | |
parent | fb5f60883f4f60a0689a01471c42efe21017d84b (diff) | |
download | gpsd-238ff98ef02863be9a8a36f6b8005f53301439e2.tar.gz |
Some ships in US waters transmit 8-bit MMSIs.
Diffstat (limited to 'www')
-rw-r--r-- | www/AIVDM.txt | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/www/AIVDM.txt b/www/AIVDM.txt index 8708e61b..99a197cb 100644 --- a/www/AIVDM.txt +++ b/www/AIVDM.txt @@ -1,6 +1,6 @@ = AIVDM/AIVDO protocol decoding = Eric S. Raymond <esr@thyrsus.com> -v1.26, July 2010 +v1.27, July 2010 This document is mastered in asciidoc format. If you are reading it in HTML, you can find the original at http://gpsd.berlios.de/AIVDM.txt[] @@ -432,9 +432,13 @@ unusual or rare; many AIS transmitters never emit them. As of November 2009, an overnight capture of a full feed from <<<AISHUB>>> shows no type 25 or type 26 messages at all. -An MMSI is a Mobile Marine Service Identifier, a unique 9-digit ID -for the ship's radio(s). The first three digits convey information -about the country in which the ID was issued <<ITU-MID>>. +An MMSI is a Mobile Marine Service Identifier, a unique 9-digit ID for +the ship's radio(s). The first three digits convey information about +the country in which the ID was issued <<ITU-MID>>. US vessels +travelling solely in U.S. waters sometimes incorrectly omit the +leading "3", the geography code for North and Centra America and +Caribbean, emitting 8-digit MMSIs beginning with the U.S. country code +of 669. Detailed descriptions of message types 1-24 follow. Message types 1-22 are derived from <<IALA>>. Message type 23 was decribed to me by Mike @@ -2059,3 +2063,7 @@ U.S. Coast Guard PAWSS messages. Version 1.26 corrects an error in describing rate-of-turn decoding in AIS Type 1, 2, and 3 messages, + +Version 1.27 describes the sometime U.S. practice of omitting the leading +'3' region code from MMSIs. + |