AIS decoded fields descriptions and their values

Learn which fields are decoded by Spire Sense and which get translated into more meaningful ship descriptions

Decoded Fields

The following fields are currently decoded within Spire Sense:

Common Fields

  • msg_type : AIS message type
  • mmsi : Marine Mobile Service Identity number for the vessel
  • timestamp : ISO8601 formatted UTC timestamp of the AIS message

Position Fields

  • accuracy : Vessel GPS geolocation accuracy, based on meters. 1 : high accuracy (≤ 10 meters), 0 : low accuracy (> 10 meters) or default
  • course : Course over ground in degrees
  • heading : Direction vessel is facing in degrees
  • latitude : Vessel latitude in degrees (North = positive, South = negative)
  • longitude : Vessel longitude in degrees (East = positive, West = negative)
  • maneuver : Indicates whether or not a vessel may be engaged in a "special" maneuver
  • rot : Vessel rate of turn in degrees per minute
  • speed: Vessel speed over ground expressed in knots
  • status: Vessel navigation status

Static Fields

  • ais_version : Vessel AIS version
  • call_sign : Vessel call sign
  • destination : Reported destination of the vessel
  • draught : Vessel draught expressed in 1/10 meters
  • eta : Estimated time of arrival for the vessel
  • imo : Vessel unique International Maritime Organization number
  • length : Vessel length
  • name : Vessel name
  • ship_and_cargo_type : Vessel ship and cargo type code
  • width : Vessel width
  • dimensions: The 4 dimensions A,B,C,D of the ship relative to it's GPS as detailed below.
  • dimension A, the distance in meters from the GPS to the bow
  • dimension B, the distance in meters from the GPS to the stern
  • dimension C, the distance in meters from the GPS to the port side
  • dimension D, the distance in meters from the GPS to the starboard side

Translated Descriptions

Since AIS messages contain several fields that must be translated into human readable descriptions, we handle this for some fields within Spire Sense for your convenience.

Ship Type

The ship_and_cargo_type  is a 2-digit number within a static AIS message that represents the type of ship it is and what it carries. Spire Sense APIs return a ship_type description derived from the ship_and_cargo_type number.

For the instance:

"ship_and_cargo_type": 80

the API would return:

"ship_type": "Tanker"

For more on ship type, check out our Determining Ship Types article.

Vessel Flag Country

Vessel Flag Country, represented via flag  and flag_short_code , is derived from the first 3 digits within the MMSI. For more on this, check out our Vessel Flag Country article.