Almost 90% of everything we buy arrives via seaborne trade, which consists of over 55,000 merchant ships, registered to 150 nations. With statistics like this, it is no wonder that “ship-tracking” and “vessel-tracking” have become far more prevalent in today’s business world. So, what exactly is vessel tracking or a vessel tracking system (VTS)?
“A vessel tracking system, as the name suggests is a collection of equipment which enable marine and naval vessels to track, identify and monitor a ship’s position, location and any other detail that might be important in maneuvering and stabilizing a ship’s route and course.” Simply put: vessel tracking is the monitoring of ship traffic around the world.
As technology continues to improve, so do the methods in which we track global vessel movements. There are a handful of different vessel tracking systems available, each with its own benefits and challenges. We will explore some of the various systems below.
The Global Positioning System (GPS) is a U.S.-owned utility that provides users with positioning, navigation, and timing (PNT) services. This system consists of three segments: the space segment, the control segment, and the user segment. The U.S. Air Force develops, maintains, and operates the space and control segments.
GPS satellites, which are in orbit around the world, broadcast radio signals of their location, status and precise time. This signal then travels through space (at the speed of light) until it reaches a GPS device on earth. Once the GPS device has received messages from four satellites is can then use geometry to determine is location on Earth.
The main limitation to GPS is that it only transmits position, velocity, and time. While GPS is the most precise and accurate radio navigation system available today, it alone is far from the most comprehensive solution for vessel tracking. However, when combined with some of the other technologies below, we can develop a much more robust vessel tracking system.
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’s strength is being able to track all vessels, including those not transmitting any radio signals (such as AIS). However, it is more expensive to install, takes more power to run, and requires some operational knowledge from the user. It also does not contain any more information aside from position, course, and speed.
Long Range Identification and Tracking (LRIT) is an international tracking and identification system incorporated by the IMO under its SOLAS convention to ensure a thorough tracking system for ships across the world. Established in 2006 by the International Maritime Organization per recommendations of the Maritime Security Committee for all SOLAS (International Convention for the Safety of Life at Sea) cargo vessels 300 gross tons or more, passenger vessels and mobile offshore drilling units. Vessels are required to report to their position four times per day or upon poll requests for an on‐demand position reporting through the flag states selected LRIT data center.
LRIT is not considered an aid to navigation since it’s information is not available to vessels in its vicinity and it operates on a closed network (operated by the flag state). It uses a call and response format and can be configured from 15 minute to 24 hour reporting frequency. LRIT transmits vessel identification information, position, time and date.
AIS, short for Automatic Identification System, is an automatic ship tracking system used onboard ships as well as onshore VTS (Vessel Traffic Service) systems to monitor vessel movements around the world.
AIS transceivers automatically broadcast positional data via VHF radio transmissions. The transceivers are connected to the ships navigational sensors, such as GNSS (global navigation satellite system) and a gyrocompass. This allows for nearly real-time updates of positional information including: Latitude/Longitude, Rate of Turn, Speed Over Ground (SOG), Course of Ground (COG), and True Heading. This positional data is sent out at regular intervals, between 2 and 10 seconds while underway and every 3 minutes while at anchor.
The second type of information sent via AIS messages are Static and Voyage Data. This information is sent out every 6 minutes and is manually entered and updated by the vessel operator. The additional set of data values are: IMO number, call sign, vessel name, vessel type, cargo type, activity, navigational status, ETA, destination, draught, length, beam, and country (flag). Instructions for inputting this data into the AIS device can be found on the USCG Navigation Center website.
There are a few different challenges with using AIS for ship tracking. AIS systems require the vessels to have a transmitter installed on-board in order to receive position updates, whereas a radar system does not. AIS receivers also have a 20-40nm range, which limits coverage past the coastline. Lastly, since AIS information is publicly broadcast, it can be subject to manipulation or “spoofing” from 3rd parties.
With so many different options to choose from when it comes to vessel tracking, it can be difficult to decide on which one to use. Fortunately, many systems today use a combination of services to provide customers with the most complete coverage possible.
Our PortVision 360 application has the ability to ingest not only AIS and Satellite AIS, but Radar feeds and LRIT Satellite trackers as well. You can use PortVision 360 to track your vessels in real-time, as well as run historical reports going back as far as 2007 in some cases.
To learn more about how PortVision 360 can help you overcome your biggest vessel tracking challenges, click on the button below!