AIS

Why it matters to yachts

Collision avoidance is the headline, but AIS delivers more. Watchkeepers see targets with names, bearings and Closest Point of Approach right on the plotter or ECDIS, which helps in restricted visibility and complex crossings. Port authorities expect AIS discipline, and many large commercial yachts must carry it under SOLAS Chapter V, which references carriage requirements tied to gross tonnage and ship type. Even when not strictly required, fitting AIS is considered best practice for internationally voyaging yachts.

Class A vs Class B, choosing the right transmitter

• Class A is mandated for most SOLAS-classed vessels. It transmits at higher power and with faster update rates, includes a display or Minimum Keyboard and Display, and is designed for the heaviest traffic environments.

• Class B is intended for smaller craft. Traditional Class B uses CSTDMA at 2 W with slower, fixed reporting intervals. Newer Class B SO, sometimes called B+, uses SOTDMA at 5 W with reserved time slots and faster updates, which makes a yacht more visible in busy lanes or at higher speeds. For performance-oriented or professionally crewed yachts that are not SOLAS-mandated, Class B SO is often the smart middle ground.

AIS Classes infographic (A vs B vs B SO)

How AIS fits into your bridge and fleet

On board, the AIS black box ties into GPS and the VHF antenna, then streams targets to your plotters via NMEA 2000 or 0183, as well as to ECDIS where fitted. Symbols and text boxes indicate dynamic data like heading and speed, plus static data like name and MMSI, and safety messages. Shore systems and Vessel Traffic Services ingest the same feed to improve coastal awareness, and space-based receivers extend visibility far offshore. The way these targets and messages should be shown on compliant displays is laid out in IALA guidance, which helps explain what your officers actually see on screen.

Regulatory snapshot for yachts

Under SOLAS V Regulation 19, ships of 300 GT and upwards on international voyages, cargo ships of 500 GT and upwards not on international voyages and all passenger ships must carry AIS. Many large commercial yachts fall into those thresholds, while private yachts below them often choose Class B voluntarily to raise their profile. Administrations also expect AIS to be in continuous operation unless a specific security or safety exception applies, so plan your procedures and privacy expectations accordingly.

Practical gains beyond avoiding close quarters

• Situational awareness, your bridge team can prioritize high-risk encounters using CPA and TCPA without waiting for a radar return from a low-RCS hull.

• Anchorage clarity, transmitting your status as “at anchor” reduces misunderstandings at night.

• Tender logistics, pairing the mothership with tenders that carry Class B units creates a cleaner operating picture near busy beaches or marinas.

• Fleet oversight, management platforms can combine AIS and satellite tracking over VSAT links for remote auditing of routes and ETAs, useful for seasonal programs and yard transits. The USCG’s AIS knowledge base summarizes many of these use cases and configuration questions.

Installation notes that matter

Antenna height is range, so mount the AIS VHF whip high on the mast or arch and keep coax runs short and dry. Give the GNSS antenna a clean sky view, and avoid metal shadowing from radars or satellite domes. Encode your MMSI and static data accurately, then verify on the bridge that symbols, alarms and “navigate to target” functions behave as expected. During sea trial after a superyacht refit, log target reception and reporting intervals to confirm performance in real traffic. The USCG Navigation Center and IALA resources provide checklists and display conventions that crews can use during acceptance.

AIS network schematic

Risk, etiquette and limitations

AIS is cooperative, so it does not replace radar for detecting targets that are not transmitting or have faulty installations. Spoofing and data errors occur, which is why bridge teams must cross-check with radar and visual bearings before maneuvering. Keep AIS on except where rules allow silencing for security, and ensure voyage status is set correctly to avoid confusing traffic services. Remember that AIS is not part of GMDSS distress alerting, although many devices, such as AIS MOB and AIS SART, use the same framework to mark persons or life rafts for local homing. For policy and operation, the IMO and USCG pages are the primary references.

Making the specification decision

Ask three questions. Are you subject to SOLAS carriage and therefore fixed on Class A. Do you run fast or operate regularly in high-density traffic, which argues for Class B SO rather than legacy Class B. Will your bridge and service provider support firmware and data audits as part of planned maintenance during yard periods. Build the answers into your refit scope and acceptance tests, with antenna, cabling and display verification included in commissioning. Regulatory texts and technical recommendations linked above give you the baseline to document this choice clearly.

AIS does not make decisions, people do. Equip the yacht with the right class, integrate it cleanly with your bridge and train the watch to trust but verify. When you can see and be seen, you buy time, and at sea, time is safety.

FAQ: AIS For Yachts

When is Class B SO worth upgrading from legacy Class B?
Choose Class B SO if you run fast, operate in busy lanes, or want more frequent position updates. It transmits at higher power with reserved time slots, so other vessels see you sooner and more reliably than with legacy Class B.

How do I verify my AIS is actually transmitting after installation or refit?
Perform a dockside check with a nearby vessel or shore station and confirm your MMSI, name, position and status appear correctly. On board, review the AIS self-test, GPS quality and VSWR/antenna alarms, then log a short sea trial to confirm update rates in real traffic.

What antenna setup gives the best AIS range on a yacht?
Height is range, so mount the VHF antenna as high as practical and keep coax runs short with quality connectors. Avoid splitters if possible, or use an AIS-approved active splitter and ensure good grounding to reduce losses.

Does AIS replace radar for collision avoidance?
No, AIS is cooperative and only shows transmitting targets. Use AIS to identify vessels and assess CPA/TCPA, then cross-check with radar and visual bearings before maneuvering.

Should my tenders carry AIS too?
Fitting Class B on frequently used or night-operated tenders improves safety near marinas and beaches. It also simplifies mothership coordination when shuttling guests or gear.

Can I turn AIS off for privacy or security?
Masters may silence AIS temporarily for security or safety, but it should be the exception, not the rule. Record the reason, restore transmission as soon as the risk passes, and coordinate with local traffic services when appropriate.

What is the difference between an AIS SART/MOB and a normal AIS transponder?
AIS SART and AIS MOB devices are emergency beacons that create a short-range, high-priority target for local homing. A standard AIS transponder continuously broadcasts the vessel’s identity and movement for routine navigation.

How do I reduce screen clutter from AIS targets in busy areas?
Use CPA/TCPA filters, range limits and target classes to focus on genuine collision risks. Keep text labels minimal, zoom thoughtfully, and acknowledge alarms promptly to prevent alert fatigue.

Will satellite AIS track my yacht offshore?
Often yes, but reception depends on traffic density and transmitter power. Treat satellite AIS as a visibility bonus, not a distress tool, and rely on GMDSS equipment like EPIRB for emergency alerting.

What routine maintenance keeps AIS reliable?
Include AIS in planned maintenance with annual checks of antenna condition, coax continuity, GNSS performance and firmware. After any yard period, re-validate MMSI and static data, then run a short operational test.

Do I need to reprogram AIS if the yacht changes name or flag?
Yes. Update the registered MMSI and static data through your flag administration or service provider, then confirm the new identity is broadcasting correctly.

Can AIS data be wrong or spoofed, and how should the bridge react?
Yes, bad installations and occasional spoofing do occur. Always cross-check AIS targets with radar plots and visual references, and treat anomalies conservatively.

Does AIS help with VHF calling and bridge-to-bridge coordination?
Absolutely. Calling another vessel by name or MMSI reduces confusion, speeds up agreements on passing, and supports clean COLREGs communications.

What AIS settings matter most for a professional bridge team?
Keep voyage status accurate, set sensible CPA/TCPA thresholds, and ensure alarms are audible at the conning position. Review these during handovers so every watchkeeper interprets AIS symbology the same way.

Where does AIS fit in a superyacht refit plan?
Integrate AIS with plotters or ECDIS, confirm interface standards, and plan cabling, antennas and splitter strategy during the design phase. Commission the system with documented acceptance tests so performance can be audited later by management companies.