FLIR and radar technology

FLIR cameras and radar units can both see things the naked eye can’t, but they operate very differently and should be considered standalone assets.

Radar stands for Radio Detection and Ranging. Invented a few years before WW2, it is still considered the single-most important piece of electronic wheelhouse equipment in the commercial maritime industry.

Under the Collision Regulations (COLREGs), if radar is fitted to your vessel and is operational, rules 5 (look out) and 7 (risk of collision) state that it must be used.

Unlike an AIS (Automatic Identification System) or a GNSS (GPS) receiver, it isn’t dependent on any third-party technology or sensors to deliver information to the watchkeeper. It determines ranges based on the unwavering speed of light and does so with consistency, independence, and accuracy.

A recent development in radar is 3G and 4G broadband technology to replace the electromagnetic high energy ‘pulse’ used by traditional radar. These broadband transmissions are uninterrupted and use both transmitting and receiving antennas at the same time, consuming far less power and energy.

They can’t detect SARTs (Search and Rescue Transponders) or racons (radar beacons) though.

Radar has two primary uses: collision avoidance and navigation.

By using the EBL (Electronic Bearing Line) feature and placing it on the target (echo) we can see if that target tracks towards us down that line – in which case, the risk of collision is obvious. The EBL measures the bearing from your boat to a target object.

Using the variable range marker tool will then give you the range to that vessel that may be on a collision course.

Most modern radars will also have a MARPA (Mini Automatic Radar Plotting Aid) function. This can also help identify any targets that present a risk of collision by displaying the closest point of approach and the time to closet point of approach of any selected target. 

Good seamanship ideally requires us to manually confirm our electronic fixes, but few of us will remember, or never learned, how to do this with a magnetic compass. This is where a radar and a paper chart can get you a position with no calculation required, just by using two or more ranges obtained by using the variable range marker from identifiable landmarks.

This is quick and accurate if the intersect of these ranges is not too oblique, you remember how to use the scale of latitude to measure distance, and you possess a pencil compass. You just scribe an arc on your chart from one range observation, then scribe another arc from your second – where they intersect is where you are.

A variable range marker can also be set up on your radar display to assist you in keeping a certain distance from dangers. Even better is the use of one or more PIs (parallel index lines). These are lines displayed on the screen either port or starboard of your heading marker (course), at a distance that you set when you made your passage plan.

Commercial mariners are trained to navigate around complex island and reef environments using only PIs so they learn to appreciate their effectiveness.

The ‘relative motion illusion’ has contributed to several marine incidents. An air traffic control tower differs significantly from a boat in that the tower is fixed, and targets on the controller’s screen all move in true motion. But while you’re motoring along in your vessel, nothing on your radar screen is showing true motion.

Imagine a target off your port bow moving towards you on a collision course. You might think this is a crossing situation and the boat should give way to you – but if you are also moving, chances are that you’re approaching the boat from its starboard quarter in a converging/overtaking situation, meaning that it’s you who should be giving way.

Modern radars will have a ‘true motion’ function, which requires other sensors to be interfaced with it, but this has disadvantages and even professional mariners use true motion display only intermittently.

FLIR stands for Forward Looking Infrared and is a relatively new technology for recreational mariners. FLIR is actually a brand name acquired by Teledyne Technologies Inc, whose market dominance has contributed to the term’s generic use to describe thermal imaging devices in the marine sector.

Don’t confuse thermal imaging with ‘night vision’, which has a distinctive greenish tinge as it amplifies any light available. Night vision (a comparably low-cost option) can create a high-contrast, difficult to interpret image in the maritime environment when even a few anchor lights can create a blinding and confusing scene.

Thermal imaging cameras, however, create images from heat rather than from light. Thermal imaging is usually identifying warmer targets against a uniformly cooler background such as water. It applies to cooler objects, too – even ice.

For the mariner, it’s a tool for rapid situational awareness. The features of a modern camera can include object detection and associated alerts, as well as gyro stabilisation, video tracking of objects, and colour thermal vision. 

Thermal cameras are a standout asset for search and rescue applications. Given that every one of us might find ourselves in a SAR situation at some point, this is worth thinking about.

Any comparison of FLIR and radar should be made based on your boating environment, your boating intentions and your budget. But as items of wheelhouse equipment, they are standalone assets.

To fully exploit its potential, radar requires more operator skill and an understanding of its operating principles. Even the most powerful radar units are still limited by the height of the scanner unit and Earth’s curvature. A radar set to 12nm range with a scanner height of 4m will only have a visible horizon of about 4.5nm.

A FLIR camera can virtually turn night into day, and allows you to identify objects, the aspects of nearby vessels, and even the activities of those on deck. The heat signatures of even semi-submerged dangers – invisible to radar – can easily be identified, as can a person in the water.

For collision avoidance, FLIR is a valuable tool for maintaining a good look out, but it can’t give you the ranges and bearings for position fixing or thorough navigational decision making.

The ability to interface technologies like radar and AIS has been a game changer in the wheelhouse, but it’s essentially still data that needs to be interpreted.

SEE THE FULL REVIEW IN THE AUGUST-SEPTEMBER 2024 (VOLUME 39.4) ISSUE OF CLUB MARINE MAGAZINE.

SUBSCRIBE TO CLUB MARINE MAGAZINE.