From 308dc77a6ee7553d21bec0f10c081907792d83cb Mon Sep 17 00:00:00 2001 From: Vladimir Rutsky Date: Wed, 10 Aug 2016 19:14:54 +0300 Subject: [PATCH] fix several typos in AIVDM documentation Signed-off-by: Vladimir Rutsky --- www/AIVDM.txt | 50 +++++++++++++++++++++++++------------------------- 1 file changed, 25 insertions(+), 25 deletions(-) diff --git a/www/AIVDM.txt b/www/AIVDM.txt index b8694fc..01cb77a 100644 --- a/www/AIVDM.txt +++ b/www/AIVDM.txt @@ -32,7 +32,7 @@ cellphones do to avoid mutual interference. AIS receivers make this data available for navigation, anti-collision systems, and other uses. The International Maritime Organization's (IMO) International -Convention for the Safety of Life at Sea (SOLAS) reqires operating AIS +Convention for the Safety of Life at Sea (SOLAS) requires operating AIS transmitters on all international cargo vessels of more than 300 tons displacement, all cargo vessels of more than 500 tons displacement, and all passenger vessels; see <> for details. Individual @@ -522,14 +522,14 @@ for a list of MIDs. |00MIDXXXX | Coastal stations |111MIDXXX | SAR (Search and Rescue) aircraft |99MIDXXXX | Aids to Navigation -|98MIDXXXX | Auxilary craft associated with a parent ship +|98MIDXXXX | Auxiliary craft associated with a parent ship |970MIDXXX | AIS SART (Search and Rescue Transmitter) |972XXXXXX | MOB (Man Overboard) device |974XXXXXX | EPIRB (Emergency Position Indicating Radio Beacon) AIS |============================================================================== Detailed descriptions of message types 1-24 follow. Message types 1-22 -are derived from <>. Message type 23 was decribed to me by Mike +are derived from <>. Message type 23 was described to me by Mike Greene based on <>. Message type 24 was described to me by <>, whose Python toolkit decodes it. Message types 25-26 are reported by <>, who observes they were added in Version 3 of @@ -993,7 +993,7 @@ in use for type 6. DAC/FID pairs are assigned separately per message type. -Note that the apparent presence of one of these DAC/FID pairs dooes +Note that the apparent presence of one of these DAC/FID pairs does not guarantee that the message is structured. Decoders should perform range validation on the structured fields and interpret the message as unstructured if any check fails. (As of Aug 2014 no such @@ -1200,7 +1200,7 @@ authority it is a berthing assignment. A message 6 subtype. DAC = 001 FID = 20. Fixed Length: 360 bits. -The 2-bit fields after "availabilty" describe services which may be +The 2-bit fields after "availability" describe services which may be available at the berth. They are valid only if this master availability bit is on. @@ -1875,7 +1875,7 @@ once. |243-247 | 5 |Spare | |x|Not used |============================================================================== -<> says of the Destunation MMSI field "a virtual MMSI number +<> says of the Destination MMSI field "a virtual MMSI number should be used for each country, each national AIS network should route messages addressed to other countries using this virtual MMSI number". @@ -2123,7 +2123,7 @@ perform range validation on the structured fields and interpret the message as unstructured if any check fails. Actual false matches with DAC/FID = 200/10 have been observed in the wild. -DAC/FID pairs 1/23, 1/28, and 1/30 have addressed versions descrubed +DAC/FID pairs 1/23, 1/28, and 1/30 have addressed versions described under type 6. FID types 11-15 are being phased out and are not to be used after 1 @@ -2249,7 +2249,7 @@ for whatever that means. The seastate field has a note in <> reading "(manual input?)"? -WMO 306 Code table 4.201 specifies the following precipitatiuon type values: +WMO 306 Code table 4.201 specifies the following precipitation type values: .Precipitation Types [width="50%",frame="topbot",options="header"] @@ -2312,9 +2312,9 @@ Described in <> but deprecated by <>. |38-39 | 2 |Spare | |x|Not used |40-49 | 10 |DAC |dac |u|DAC = 001 |50-55 | 6 |FID |fid |u|FID = 13 -|56-175 |120 |Reason For Closing |reason |t|20 6-bit characcters -|176-295 |120 |Location Of Closing From|closefrom|t|20 6-bit characcters -|296-415 |120 |Location of Closing To |closeto |t|20 6-bit characcters +|56-175 |120 |Reason For Closing |reason |t|20 6-bit characters +|176-295 |120 |Location Of Closing From|closefrom|t|20 6-bit characters +|296-415 |120 |Location of Closing To |closeto |t|20 6-bit characters |416-425 | 10 |Radius extension |radius |u|0-1000, 10001 = N/A (default) |426-427 | 2 |Unit of extension |extunit |u|0=m, 1=km, 2=nm, 3=cables |428-432 | 5 |From day (UTC) |fday |u|1-31, 0=N/A (default) @@ -3321,7 +3321,7 @@ The standard does not fix the meaning of a water temperature depth of 127. 504-511 reserved. |45-46 | 2 |Salinity Type |salinitytype|e|0 = measured, 1 = calculated using PSS-78, - 2 = calclated using other method, + 2 = calculated using other method, 3 = reserved. |47-49 | 3 |Sensor Description |sensortype |e|See "Sensor Types" |50-84 | 35 |Spare | |x|Not used @@ -3350,8 +3350,8 @@ No default is specified for salinity type. 244-255 reserved. |24-33 | 10 |Dew Point |dewpoint |i|-20.0 to +50.0: 0.1 deg C, 501 = N/A (default), - 502-511 rsserved, - -511--201 rsserved. + 502-511 reserved, + -511--201 reserved. |34-36 | 3 |Dewpoint Sensor Type|dewtype |e|See "Sensor Types". @@ -3666,7 +3666,7 @@ expand both. Full ERI codes have been observed in the wild. |8250 | 79 | Pushtow, five cargo barges |8260 | 79 | Pushtow, six cargo barges |8270 | 79 | Pushtow, seven cargo barges -|8280 | 79 | Pushtow, eigth cargo barges +|8280 | 79 | Pushtow, eight cargo barges |8290 | 79 | Pushtow, nine or more barges |8310 | 80 | Pushtow, one tank/gas barge |8320 | 80 | Pushtow, two barges at least one tanker or gas barge @@ -3826,7 +3826,7 @@ messages. |56-67 | 12 |UN Country Code |country |t|2 six-bit characters |68 | | |gauges |a4|Gauge measurement array |0-10 | 11 |Gauge ID |id |u|0=unknown (default) -|11-24 | 14 |Water Level |level |i|cm, 0=unknown (defailt) +|11-24 | 14 |Water Level |level |i|cm, 0=unknown (default) |=============================================================================== Water levels are relative to the local standard, e.g. GIW in Germany @@ -4079,7 +4079,7 @@ one message type. Length is 160 bits. Message type 16 is used by a base station with control authority to configure the scheduling of AIS informational messages from -subordinate stations, either as a frquency per 10-minute interval or +subordinate stations, either as a frequency per 10-minute interval or by specifying the TDMA slot(s) offset on which those messages should be transmitted. It is probably not of interest unless you are studying the internal operation of an AIS base station network. @@ -4418,7 +4418,7 @@ network. |============================================================================== The values of the channel_a and channel_b fields are ITU frequency -designators for channelas A and B. Normally these will be 2087 and +designators for channels A and B. Normally these will be 2087 and 2088, the AIS 1 and AIS 2 frequencies of 87B (161.975 MHz) and 88B (162.025 MHz) respectively. Regional authorities may set different frequencies. @@ -4481,7 +4481,7 @@ station network. The target set of mobile stations is specified by the station-type and ship-type fields. An addressed (non-broadcast) message 22 overrides a -message 23, but a message 23 ovewrrides a broadcast message 22. +message 23, but a message 23 overrides a broadcast message 22. Note that the 'not available' values for longitude and latitudes match the short ones used in messages 17 and 22, not the long ones @@ -4552,7 +4552,7 @@ used to associate an MMSI with a name on either class A or class B equipment. A "Type 24" may be in part A or part B format; According to the standard, parts A and B are expected to be broadcast in adjacent pairs; in the real world they may (due to quirks in various -aggregation methods) be separated by other sentances or even +aggregation methods) be separated by other sentences or even interleaved with different Type 24 pairs; decoders must cope with this. The interpretation of some fields in Type B format changes depending on the range of the Type B MMSI field. 160 bits for part A, @@ -4610,7 +4610,7 @@ dimensions as in Message Type 5. According to <>, an MMSI is associated with an auxiliary craft when it is of the form 98XXXYYYY, where (1) the '98' in positions 1 -and 2 is required to designate an auxilary craft, (2) the digits XXX +and 2 is required to designate an auxiliary craft, (2) the digits XXX in the 3, 4 and 5 positions are the MID (the three-digit country code as described in <>) and (3) YYYY is any decimal literal from 0000 to 9999. @@ -4681,7 +4681,7 @@ note "Allows for 32 bits of bit-stuffing." The 20 radio status bits are always present after end-of-data in the last slot and are in the format specified by <>. The radio status is 20 bits rather than 19 because an extra first bit selects -whether it should be interpretred as a SOTDMA or ITDMA state. +whether it should be interpreted as a SOTDMA or ITDMA state. i Note: Type 26 is extremely rare. As of April 2011 it has not been observed even in long-duration samples from AISHub. @@ -4804,7 +4804,7 @@ the type of AIS equipment. Beginning with NMEA 4.10, the standard describes a way to intersperse "tag blocks" with AIS sentences in order to supply additional -metadata, udually a Unix timestamp to be associated with a sentence +metadata, usually a Unix timestamp to be associated with a sentence (or contiguous group of sentences such as an armored AIS Type 5). The tag block facility is complex, in some respects poorly specified, @@ -4893,7 +4893,7 @@ One is an apparent error in the format design. The type 15 message has a variant with 108 data bits and a trailing 2-bit spare field, for 110. This spare should have been 4 bits to guarantee a byte boundary at 112 bits. Decoders need to be prepared to encounter this length -in case the transmitter has implemented the padding reqirement +in case the transmitter has implemented the padding requirement properly. The other is messages containing variable-length text packed into @@ -4992,7 +4992,7 @@ Free San Francisco Bay Area AIS feed. For non-commercial use only. Here is an application of the JSON metaformat to present AIS data in a form more convenient for application use than AIVDM/AIVDO sentences. This encoding is implemented by GPSD and its client libraries. It is -decribed here because (a) the specification is closely tied to the +described here because (a) the specification is closely tied to the field encodings, and (b) the author wishes to offer it as an interoperability standard for other applications. -- 2.7.4