AIS interface

Last Updated on Thursday, 07 October 2010 08:37 Written by Alison Little Thursday, 18 March 2010 14:11

AIS is a short range tracking protocol which allows vessels and vessel traffic systems (VTS) to exchange information on other ships and VTS stations. The information is sent over VHF radio; in order to ensure that the VHF transmissions of different transponders do not occur at the same time the signals are time multiplexed using a technology called Self-Organized Time Division Multiple Access (STDMA). A ship will transmit AIS data about its own identity, position and course; it may also receive AIS data via an AIS receiver which receives and decodes the VHF signals and passes the information on to chart displays.

Ship Sim simulates an AIS receiver, outputting the AIS data for target vessels defined within Ship Sim. The serial data is output in encapsulated VDM format, as used by most AIS receivers and compatible with suitable chart plotters.

AIS data includes the following:

• Navigation status – "at anchor", "under way using engine(s)", etc
• Speed over ground, Course over ground, True Heading
• Longitude and Latitude
• Time stamp
• IMO ship identification number
• Radio call sign
• The vessel's Maritime Mobile Service Identity
• Ship name
• Type of ship/cargo
• Dimensions of ship
• Destination
• Estimated time of arrival at destination.

Ship Sim 3 AIS Test Simulator

Ship Sim 3 obtains the AIS data from the target information and from the information entered on the Target Manager dialog.

Targets are extra vessels which can be defined by the user and set to follow courses or tracks. They may output NMEA TLL messages and AIS messages, which send more information on the target’s course and intended destination. Target data is also transmitted by the Radar interface. Targets can also be controlled from outside Ship Sim by TLL messages.

Target types are as follows:

• A Simple target a vessel defined with a starting position, heading and speed,
• ‘Track’-type targets can be defined to drive round a series of waypoints, either via a track defined by straight lines and radiused bends, or defined using Bezier curves.

The targets can be set to crab depending on the applied tide.

Ship Sim can also receive and decode AIS messages.