Marine Navigation FAQ

Yes, for any boat operating offshore, at night or in poor visibility. AIS only shows vessels that are transmitting. Radar independently detects physical reflective targets, including small non-AIS fishing boats, unlit yachts, buoys and rain squalls. They answer different questions and the strongest offshore picture uses both.

Viewing distance matters more than hull length. Roughly: 7 to 9 inches on a 4 to 6 m trailer boat, 9 to 12 inches on a 30 to 38 ft yacht, 12 to 16 inches on a 38 to 48 ft yacht or offshore fishing boat, 16 inches or more on a motor-yacht glass helm. For many 35 to 45 ft cruising yachts, 12 inches is the sweet spot — and a good 12-inch display with radar, AIS and accurate heading beats a very large screen fed by weak sensors.

ACMA's maritime ship station class licence allows eligible operation of specified maritime equipment on standard frequencies including VHF, and ACMA states users do not apply or pay a fee for it. You must still comply with its conditions and hold an appropriate operator qualification, or operate under the supervision the conditions allow. MF/HF and some other operations can require different maritime ship licensing. Australia's framework changed in 2025, so confirm the current position with ACMA rather than relying on older advice.

No, not on its own. Satellite broadband is genuinely useful for weather, email and remote work, but it needs power, working terminal hardware, a subscription and network service. Keep emergency communication diversified and independent: fixed VHF, a charged handheld VHF, a registered EPIRB and a handheld satellite messenger that survives a vessel electrical failure.

Not if they share power, GNSS source, NMEA backbone and software ecosystem. That gives operational convenience and display redundancy, but a single breaker, battery bank or network fault can still remove both. Genuine redundancy means a navigation method that remains useful after a network or primary-power failure — typically a tablet with offline charts stored charged and disconnected, plus a magnetic compass.

Fix DC power integrity first, because new electronics on poor wiring are still unreliable electronics. Then safety communications — DSC VHF with the correct MMSI and a registered beacon. Then one good display with a properly specified and sited transducer. Then, in mission order: AIS, a heading upgrade, radar, and finally autopilot capability or advanced sonar.

It varies enormously, which is why Zone of Confidence exists. Major ports and shipping approaches receive intensive survey attention; the Kimberley, Cape York, the Gulf of Carpentaria, remote islands and less frequently surveyed reef areas can contain much older data. A new chartplotter does not make an old survey new, so read the ZOC and widen your margins where confidence is low.

Almost always the depth offset. A sounder measures from the transducer face, and what the display shows depends entirely on the configured offset — it may be reading depth below transducer, depth below keel or total water depth. Verify it against a known depth in calm water, set it deliberately, and label the convention beside the display so the whole crew reads the same number the same way.

For standard NMEA 2000 data — position, heading, wind, depth, AIS, engine and tank data — yes, and mixed systems work well. It becomes difficult when you expect cross-brand radar, detailed sonar imagery, camera control or autopilot commissioning, because those travel over proprietary Ethernet. Choose one primary ecosystem for the high-bandwidth sensors, then integrate specialist devices around it.

For a new offshore cruising system in 2026, generally yes where budget permits. SOTDMA can bring improved slot management, higher transmission power on many units and more frequent reporting in relevant situations, all of which matter most when you want to be seen reliably in busy or distant water. For sheltered coastal use, a good CSTDMA Class B unit remains perfectly serviceable.

No. The Australian Hydrographic Office notes that systems able to use S-101, S-102, S-104 and S-111 products will initially be limited. Buy equipment that solves today's navigation problem. On a large premium refit it is reasonable to ask the manufacturer about its S-100 roadmap, but it is not a reason to defer a needed upgrade.

From displacement, rudder area and balance, steering geometry, hydraulic cylinder volume where applicable, and the maximum steering load you expect in the worst realistic conditions — never from length alone. A heavy 40 ft cruiser can need far more drive force than a light 40 ft racer. The drive is the muscle; an excellent pilot computer cannot compensate for an undersized or badly mounted one.

It depends on your state or territory and how far offshore you operate, and the requirements change. New South Wales, for example, requires a chart and compass on open waters — explicitly noting that a compass is still required where satellite navigation is carried — and marine radio for relevant operations two nautical miles or more from shore. Always confirm current requirements with your state or territory maritime authority and AMSA.

Yes. AMSA operates the Australian beacon registration service and registration is required. An unregistered beacon still generates an alert, but registration means rescue authorities immediately know the vessel, its description and who to contact, which speeds and focuses the response. Keep it current when you sell the boat or change contact details, and check the battery expiry as part of pre-passage preparation.

Because the alarm radius was almost certainly set from the boat's position rather than the anchor's, so the real swing circle is larger than the alarm circle. The radius needs to cover anchor-to-stern distance at full scope, plus GNSS scatter. Mark the anchor position when it goes down, drop back, then set the alarm centred on the anchor.

Annually, and after any mast, antenna or heading-sensor work. Overlay radar on the chart in clear daylight near a well-charted coastline: a consistent rotational offset points to heading misalignment or a radar bearing offset. Correct the heading source first, because otherwise a heading error gets compensated into the radar and reappears later.

The engineering principles are; the product advice is not. Raymarine launched Axiom 2 in March 2026, Garmin introduced Signal VHF in May 2026 and announced SmartDrive in September 2026, Garmin launched LiveScope 2 in July 2026, B&G introduced Zeus SRX during 2026, and Simrad's NSS 4 represents a new generation of hybrid-control MFD. Australia has also begun its transition toward S-100. Model-level recommendations from 2021 are materially out of date.

Not for a conventional fibreglass coastal cruiser, where a well-sited solid-state magnetic sensor is usually sufficient. A multi-antenna GNSS compass earns its cost on steel and aluminium vessels, large catamarans, premium radar installations, boats needing stable heading at zero speed, and any vessel with a difficult magnetic environment.

Three things, cheap on any budget: a charged handheld VHF with an independent battery, a registered distress beacon that is in date, and a tablet or phone with fully downloaded offline charts stored charged and disconnected from the vessel's network. Together they cover local distress alerting, satellite distress alerting and navigation after a total electrical failure.

Not immediately before. Update to a current stable release well ahead of time, re-verify source selection and calibration afterwards — updates have been known to reset both — and get sea time on the configuration you will actually rely on. Then leave it alone.