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author | Eric S. Raymond <esr@thyrsus.com> | 2009-11-30 01:37:49 +0000 |
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committer | Eric S. Raymond <esr@thyrsus.com> | 2009-11-30 01:37:49 +0000 |
commit | a25d9a2036f3e43276353ca81586d0e4e4f6d4ec (patch) | |
tree | e8885cc6ff9aaad5e8039ec66a091b833c80ea36 /www | |
parent | f431ff9d1b054bfbcddd801c926ec2f9e6e730fa (diff) | |
download | gpsd-a25d9a2036f3e43276353ca81586d0e4e4f6d4ec.tar.gz |
Document that a trailing @ should terminate a packed-six-bit AIS string.
Ensure that both decoders do this.
Diffstat (limited to 'www')
-rw-r--r-- | www/AIVDM.txt | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/www/AIVDM.txt b/www/AIVDM.txt index d1ef3957..79969a82 100644 --- a/www/AIVDM.txt +++ b/www/AIVDM.txt @@ -1,6 +1,6 @@ = AIVDM/AIVDO protocol decoding = Eric S. Raymond <esr@thyrsus.com> -v1.16, Nov 2009 +v1.17, Nov 2009 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[] @@ -299,9 +299,11 @@ brackets, pipe bar, tilde and DEL cannot be encoded. ----------------------------------------------------------------------------- According to the standard, trailing unused characters in six-bit -fields will be represented by "@" (six-bit zero). It is common to -space-fill the fields instead, so a decoder should strip trailing -spaces well as at-signs. +fields will be represented by "@" (six-bit zero). The terminating "@" +should not be considered part of the text, and any non-"@" characters +adter it should be discarded. It is common to space-fill the fields +instead, so a decoder should strip trailing spaces well as at-signs +and garbage after them. == AIVDM/AIVDO Payload Interpretation == @@ -1548,3 +1550,5 @@ corrected it because it confused someone working on a Python decoder. Version 1.16 incorporated various minor fixes and corrections from Neal Arundale. One 'standard' fieldname changed, in message type 21: type -> aid_type. + +Version 1.17 clatfies the role of @ as a terminator in 6-bit text. |