Mariners Must Use Layered Approach To Detect Hazards

By Capt. Stephen Polk, AFNI

Director, Center for Maritime Education, Seamen’s Church Institute

Every safe voyage depends on more than a single tool; it depends on how well a watchstander builds a complete picture using all available information. In today’s busy and complex waterways, relying on radar, Automatic Identification System (AIS) or visual observation alone can leave critical gaps. When vessels find themselves in close-quarters situations, the difference between a near miss and a collision is often measured in seconds.

At the Seamen’s Church Institute’s Center for Maritime Education (CME), we emphasize that safety on the water requires commitment and proactive effort. It is built on discipline, sharp situational awareness and the ability to bring all available tools together. It’s common for watchstanders to fall into the habit of relying too heavily on a single source of information, whether that’s radar, AIS or visual observation. Each tool is valuable, but none is complete on its own.

When I reflect on my own personal experience in the U.S. Navy Reserve and with the Naval Coastal Warfare Group, this lesson was reinforced early. In port security and escort operations, we never assumed that one system would give us everything we needed. The only way to stay ahead of a threat was to build layers—overlapping sources of information that confirmed, supported and sometimes challenged one another. That same mindset applies directly to navigation in the wheelhouse.

Radar is often the starting point, but it only becomes truly effective when it is used actively. Through the Running CPA, published by Capt. John Moyle, more commonly called the Equivalent Systematic Observation, or ESO, which is taught at SCI , the radar shifts from being a passive display to a tool for critical decision-making. By carefully watching how a contact’s bearing and range change over time, a mariner can quickly recognize whether risk is developing. If the bearing stays steady while the range decreases, the situation demands attention.

AIS provides insight into a vessel’s identity and intentions, such as who it is, where it’s going and how fast it’s moving. This helps watchstanders interpret how an encounter is developing and apply the Rules of the Road — recognized navigation rules that govern how vessels interact — with greater confidence. However, AIS is only as dependable as the data entered into it, and not all vessels transmit it.

One of the most valuable features within AIS is the use of vectors, especially relative vectors. While true vectors show how vessels are moving over the ground, relative vectors reveal something more important for collision avoidance by showing how those vessels are moving in relation to you. They make developing risk easier to recognize and help a watchstander understand how changes in course or speed will influence the situation.

Then there are target trails, a tool often overlooked but incredibly powerful. Trails show where a vessel has been, turning movement into something visible and immediate. In busy or confined waters, short trails allow a watchstander to quickly recognize direction, speed and maneuvering behavior without needing to interpret numbers or wait for calculations.

Individually, each of these tools has limitations. Radar can be affected by weather or improper setup. AIS depends on human input and proper configuration. Automated tracking systems can lag or introduce errors. But when they are used together, those limitations begin to cancel each other out. One system verifies another. One fills in what another cannot provide. This is where true situational awareness is built; not from any single piece of equipment, but from the deliberate combination and assessment of all of them.

The effectiveness of wheelhouse technology ultimately rests on the training, discipline and judgment of the mariner behind it. At the Center for Maritime Education, this approach reflects our broader commitment to mariner safety and safe navigation and continues to guide our work with maritime partners across the industry.