simpleais 0.7.3

Library usage

Here’s an example, a simplified version of the aist tool, which prints one line per complete AIS message:

for sentence in sentences_from_sources(sys.argv[1:):
    result = []
    if sentence.time:
        result.append(sentence.time.strftime(TIME_FORMAT))
    result.append("{:2}".format(sentence.type_id()))
    result.append("{:9}".format(str(sentence['mmsi'])))
    location = sentence.location()
    if location:
        result.append("{:9.4f} {:9.4f}".format(location[0], location[1]))
    if sentence.type_id() == 5:
        result.append("{}->{}".format(sentence['shipname'], sentence['destination']))

    print(" ".join(result))

The sentence_from_sources() function will pull from a wide variety of sources (local files, serial ports, HTTP URLs), yielding only complete sentences as they arrive. Each sentence has a wide variety of readable information. Documented fields can all be referred to by name. For example, sentence['mmsi'] or sentence['shipname']. The location() method will return a tuple of the form (longitude, latitude). Missing or invalid fields will return None.

Command-line usage

Suppose you have a file with a bunch of AIS data from the San Francisco area. You’d like to pull out location transmissions from various sorts of ships and then plot a map of signal density. Further, you’d like to mark the locations of Fort Point and Fort Mason with asterisks just so you have some idea of what you’re seeing. To do that, you can use aisgrep to get the relevant packets and aisinfo to plot the map:

$ aisgrep -t 1 -t 2 -t 3 -t 5 -t 18 -t 19 bayarea.ais | \
aisinfo --map --point -122.4775 37.8108 --point -122.4321 37.8065

Found 51 senders in 15419 good sentences with 39 invalid (0.25%).
      top left: -122.9261, 37.9233
  bottom right: -122.3013, 37.5967
         width: 55.06 km
        height: 36.33 km
+------------------------------------------------------------+
|                                            .   .           |
|                                                 .          |
|                                             . . ..         |
|                                         ..1... ....        |
|                                           ...........      |
|                                          ......1... ..     |
|                                       ....*..1*19.....     |
|        .                          ......          . ..    .|
|              .....          .......                        |
|                   . .........                              |
|                       ...                                  |
|                    ... .                                   |
|                 ....  .                                    |
|                ..     .                                    |
|                       .                                    |
|          ..                                                |
|                                                            |
|                                                            |
|.                                                           |
+------------------------------------------------------------+

Sources

My main source for protocol information is here: http://catb.org/gpsd/AIVDM.html

More protocol info is here: http://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1371-5-201402-I!!PDF-E.pdf

The protocol checksum is here: https://en.wikipedia.org/wiki/NMEA_0183