AIS vs Radar: Vessel Tracking Options

Posted by Aaron Kline

AIS Radar

What is AIS Tracking?

Automatic Identification System (AIS) tracking is a method of contact identification and analysis used by vessel operators to avoid collisions at sea.  Most commercial vessels are required by regulation to transmit an AIS signal on the VHF marine band which includes information such as the ship’s name, position, call sign, course and speed.  Vessel owners can purchase an AIS transceiver that will translate the signal and plot the positional data on an Electronic Chart Display and Information System (ECDIS) or any number of marine charting platforms.  The vessel captain has a common operational picture of their surroundings and can use this information to safely navigate and identify vessels that may pose a risk of collision.

AIS tracking has evolved beyond a vessel-based, collision avoidance platform.  AIS data is now available to the general public and can be accessed via an internet browser.  Marine stakeholders now use AIS data for fleet and cargo tracking, demurrage validation, forecasting and conflict management, risk management and accident investigation.        

What is Radar Tracking?

Radio Detection and Ranging (radar) tracking was originally developed during WWII to track enemy aircraft but has been utilized by the maritime industry for decades.  Radar systems use radio waves that interact with objects in order to establish a bearing and range. The system generates a radio pulse which is transmitted through an antenna at a certain interval.  The pulse interacts with objects and returns to the antenna where it is processed and sent to a display. This information can be displayed on a typical radar display or represented on plotting programs which will display the contact relative to features on a marine chart.  Most radar systems have algorithms that calculate a contact’s course and speed after the bearing and range information is received over a period of time. These systems can also calculate the closest point of approach (CPA) and the time to CPA which is critical for preventing collision.  Radar systems vary in size, price and features and can be installed on any size vessel or platform.

Is AIS Tracking Better Than Radar?

AIS vessel tracking may or may not be better than radar depending on the intentions of the user.  If the user is shore based and is simply looking for a ship locator platform, AIS vessel tracking can provide accurate arrival and departure information as well as user defined alerts to provide transparency for all stakeholders.  AIS data gives you the exact time a vessel has arrived or departed the sea buoy or dock, which allows users to validate demurrage claims. Shore based chartering and trading teams can use historical AIS data that providers have been collecting and storing since its inception. With terrestrial and satellite AIS data combined, there are tens of billions of vessel positions available that can be uploaded and processed into a number of different systems, allowing for predictive analytics and forecasting of vessel traffic.  AIS information can also feed Vessel Traffic Services (VTS) for port and terminal operators. VTS is used to help manage and optimize vessel movements with AIS information providing traffic awareness and information about the configuration and movements of ships, even during times of low visibility. VTS, legal and enforcement teams can also use AIS information to reconstruct vessel movements during accident and incident investigations.

Vessel based AIS users can track marine traffic in real time thereby reducing the risk of collisions during transits.  AIS tracking information such as course, speed and range is used by vessel operators to safely navigate in the vicinity of other vessels.  AIS also provides vessel identification, enhancing the ability of captains to communicate with other vessels to establish intentions and to coordinate maneuvers in restricted waters.  Non-commercial vessels can use AIS tracking during ocean transits to reduce the risk of collisions in shipping lanes and AIS receivers draw much less power than radar systems which is critical for sailing vessels.  Non-commercial vessels can also install an AIS transceiver which functions as a transponder as well as a receiver, automatically notifying other vessels of their position.

The best alternative may be to combine inputs from both AIS and radar for a more effective vessel tracking system.  From an onshore perspective, this is a key strategy for Asset Protection services.  Onshore personnel using AIS tracking can correlate targets with offshore personnel using radar and the full team can coordinate response actions.  Vessel crews should be using every data source available to reduce the risk of collisions at sea, including AIS and radar data. There are numerous displays that will integrate radar and AIS data for both commercial and non-commercial vessels.    

When Radar Tracking May be Better Suited For You

Radar tracking is critical to vessel navigation and collision avoidance and in some cases, may be the best option for analyzing marine traffic.  Not every vessel is required to transmit an AIS signal and not every vessel required to transmit will comply. Radar vessel tracking is fundamental for risk mitigation in low visibility, especially in coastal areas due to its response time and ranging capabilities.  AIS information is delayed and also may have some positional errors. As a result, AIS is not able to effectively track fast moving vessels in restricted waters such as high speed ferries from a collision avoidance aspect but radar systems can respond quickly enough for vessel operators to gain situational awareness.   Each vessel owner/operator should consider the risks applicable to their situation in order to choose a vessel tracking strategy.

Discover PortVision AIS Tracking

Posted on Jul 31, 2018 6:07:00 AM

Topics: AIS, Vessel Tracking, Asset Protection, Radar