RYA Radar Course

Learn to use marine radar effectively for navigation and collision avoidance in restricted visibility.

Course Overview

What is it?

The RYA Radar Course teaches you how to set up, tune, and interpret a marine radar display. You will learn to use radar for navigation, collision avoidance, and pilotage in poor visibility conditions.

Who needs it?

Skippers and crew who navigate in areas prone to fog, heavy rain, or night passages. Strongly recommended for anyone planning offshore or commercial work.

Duration

1 day (shore-based)

Cost Range

GBP 150 – 250

Prerequisites

RYA Day Skipper theory or equivalent knowledge recommended

What you learn

Radar setup, tuning, and controls
Interpreting radar displays and identifying targets
Collision avoidance using radar (IRPCS / ColRegs)
Radar plotting and closest point of approach (CPA)
Limitations of radar and common pitfalls

Certification

RYA Radar Course Certificate

Radar Fundamentals

Understand how marine radar works, from pulse transmission to echo reception, and learn to operate the key controls.

Marine radar (Radio Detection And Ranging) works by transmitting short pulses of microwave energy from a rotating antenna. When these pulses strike a target such as land, another vessel, or a buoy, a portion of the energy is reflected back to the antenna. The radar measures the time delay between transmission and reception of the echo to calculate the range of the target, and uses the antenna's bearing at the moment the echo is received to determine direction.

Key components of a marine radar system

Magnetron — the high-power vacuum tube that generates the microwave pulses. It produces very short bursts of energy (typically 0.05 to 1 microsecond duration) at extremely high power.
Antenna (scanner) — the rotating bar or array mounted on the mast or arch. It focuses the transmitted energy into a narrow horizontal beam and rotates at 20-30 RPM to sweep 360 degrees.
Transmit/Receive (T/R) switch — rapidly switches the antenna between transmitting and receiving modes, protecting the sensitive receiver from the high-power transmitted pulse.
Receiver — amplifies the very weak returning echoes and processes them for display.
Display unit — shows the processed echoes as bright spots or shapes on a circular screen (PPI — Plan Position Indicator), with your vessel at the centre.

The speed of radio waves is approximately 300,000 km/s (the speed of light). A radar pulse travelling to a target 1 nautical mile away and back takes roughly 12.4 microseconds. The radar uses this time delay to calculate the target's range with high accuracy.

Modern marine radars operate on two main frequency bands. X-band radar uses frequencies around 9.3 GHz (wavelength approximately 3 cm) and is the most common on recreational and small commercial vessels. S-band radar operates around 3 GHz (wavelength approximately 10 cm) and is typically found on larger commercial ships. X-band provides better resolution and target discrimination due to its shorter wavelength, but S-band performs better in heavy rain and sea clutter because its longer wavelength is less affected by precipitation.

Exam Tip: Remember: X-band = better resolution but more clutter in rain. S-band = better rain penetration but lower resolution. Most yachts carry X-band radar only.

Interpreting the Radar Display

Learn to identify genuine targets, recognise false echoes, and understand the limitations of radar detection.

One of the most important skills in using radar is correctly identifying what the echoes on your screen actually represent. Different types of targets produce different radar signatures, and with practice you can learn to distinguish between land, vessels, buoys, and weather.

Common target types and their radar appearance

Coastline — appears as a solid, continuous line. Cliffs and steep rocky shores give strong returns. Low-lying sandy beaches may produce weak or no return. The radar coastline may not match the charted coastline exactly because radar reflects off whatever is above the waterline.
Large vessels — produce strong, bright echoes. The size of the echo does not directly correspond to the size of the vessel because radar return depends on the target's radar cross-section (shape, material, and aspect).
Small vessels — may produce intermittent or weak echoes, especially wooden or fibreglass boats. They can easily be lost in sea clutter. A yacht at close range in rough seas can be very difficult to detect.
Navigation buoys — metal buoys with radar reflectors give good returns. However, many buoys are small and may only appear at closer range scales. A cardinal buoy with a top-mark and reflector is usually easier to detect than a small lateral mark.
Rain and snow — appear as diffuse, amorphous patches on the display. Heavy rain can completely obscure targets behind it. Rain clutter is typically more problematic on X-band radar.
Bridges and overhead structures — produce strong returns but can create confusing echoes with multiple reflections underneath.

Radar reflectors work by bouncing the radar signal back toward the transmitting vessel. The octahedral (corner) reflector is the most common type carried on yachts. It should be mounted as high as possible, at least 4 metres above sea level, in the 'catch rain' orientation for maximum effectiveness.

The strength of a radar echo depends on several factors: the range to the target, the target's size and material (metal gives stronger returns than wood or fibreglass), the target's shape (flat vertical surfaces facing the radar give the strongest return), and the prevailing sea and weather conditions. A large container ship will be visible at much greater range than a sailing yacht of similar actual distance.

Exam Tip: Never assume that because you cannot see a target on radar, it is not there. Small vessels, especially wooden or fibreglass ones without radar reflectors, may not appear on your display even at close range.

Collision Avoidance with Radar

Apply radar techniques to assess risk of collision, determine CPA and TCPA, and take appropriate avoiding action in accordance with the ColRegs.

The International Regulations for Preventing Collisions at Sea (ColRegs / IRPCS) make specific reference to radar in several rules. Anyone using radar for collision avoidance must understand how these rules apply.

Key ColRegs rules relating to radar

Rule 5 (Look-out) — every vessel shall maintain a proper look-out at all times by all available means, including radar, to make a full appraisal of the situation and risk of collision.
Rule 6 (Safe Speed) — in determining safe speed, a vessel with operational radar shall consider the characteristics, efficiency, and limitations of the radar equipment; any constraints imposed by the radar range scale in use; the effect of sea state, weather, and other sources of interference on radar detection; the possibility that small vessels and other objects may not be detected at adequate range; the number, location, and movement of vessels detected by radar.
Rule 7 (Risk of Collision) — if there is any doubt about whether risk of collision exists, such risk shall be deemed to exist. Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning and radar plotting or equivalent systematic observation of detected objects.
Rule 8 (Action to Avoid Collision) — any action taken to avoid collision shall be positive, made in ample time, and large enough to be readily apparent to another vessel observing visually or by radar.
Rule 19 (Conduct in Restricted Visibility) — applies to vessels not in sight of one another in or near restricted visibility. A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing or risk of collision exists. If so, she shall take avoiding action in ample time.

Rule 19 is different from the crossing, overtaking, and head-on rules (Rules 12-18) which only apply when vessels are in sight of one another. In restricted visibility, there is no stand-on vessel — every vessel must take action to avoid a close-quarters situation, regardless of relative position.

Rule 19 also provides specific guidance: if avoiding action consists of an alteration of course, so far as possible avoid altering course to port for a vessel forward of the beam (other than for a vessel being overtaken), and avoid altering course toward a vessel abeam or abaft the beam. These rules exist because in restricted visibility, you cannot know what the other vessel is doing, so predictable, seamanlike action is critical.

Exam Tip: You must know the key radar-related ColRegs rules. In particular, understand the difference between collision avoidance in sight of each other (Rules 12-18, where stand-on/give-way applies) and in restricted visibility (Rule 19, where both vessels must act independently to avoid a close-quarters situation).

Radar for Pilotage and Navigation

Use radar as a navigation tool for position fixing, parallel indexing, clearing lines, and safe pilotage in restricted visibility.

Radar is an excellent tool for fixing your position, particularly when visual bearings are not available due to poor visibility. You can obtain a position fix by taking ranges and bearings from identifiable charted features such as headlands, breakwaters, islands, and prominent buildings or structures.

Methods of radar position fixing

Range and bearing from a single object — use the VRM and EBL to measure the range and bearing to a clearly identified charted feature. This gives a fix from a single observation, though its accuracy depends on the quality of the bearing measurement (radar bearings are typically less accurate than radar ranges).
Two or more radar ranges — the most accurate radar fix method. Take VRM ranges to two or three identifiable charted objects. Plot the range arcs on the chart; your position is where they intersect. This avoids the less accurate bearing measurement entirely.
Range and bearing from two different objects — take a range from one object and a bearing from another to produce two position lines that cross at your position.
Combination with other aids — use a radar range to one object combined with a visual bearing or depth contour to improve fix quality.

Radar ranges are generally more accurate than radar bearings. A range measured by VRM is typically accurate to within 1-2% of the range scale in use, whereas a radar bearing may have an error of 2-4 degrees or more, depending on the beam width and the type of target. For this reason, fixes based on two or three radar ranges are preferred over those using bearings.

When identifying charted features on radar, you must be careful to correlate the radar image with the chart accurately. The radar coastline may differ from the charted coastline because radar reflects off whatever is physically above the waterline (trees, cliffs, buildings), while the chart shows the high-water mark. In areas with extensive drying sandbanks or mudflats, the radar coastline at low tide may be significantly seaward of the charted high-water line.

Exam Tip: When fixing your position using radar ranges, choose objects that give a good angle of cut between the position lines — ideally 60 to 120 degrees apart. Objects that are nearly in line will give a poor fix because the range arcs will intersect at a shallow angle, making the position uncertain.