AIS for Boats UK
AIS for Boats UK — What It Is, Why You Need It, and the Best Units to Buy
At night offshore, AIS is the single most useful piece of navigation equipment on the vessel. You can see every AIS-equipped ship around you — their name, their heading, their speed, and whether they are on a collision course — before you can see their lights. That changes everything about night passages. I’ve actually been in a situation on a night watch, if it wasn’t for my beady eyes, I wouldn’t have noticed the tiny Green Starboard light on one of the smallest sailing yachts i have ever seen!
What Is AIS and What Does It Actually Do?
AIS stands for Automatic Identification System. Think of it as a GPS tracker combined with a name badge that every vessel broadcasts continuously on VHF radio frequencies.
Your AIS unit takes your position, speed, course, and heading — along with your vessel name and MMSI number — and broadcasts all of it automatically to every AIS-equipped vessel and shore station within range. At the same time it receives the same information from every other transmitting vessel and displays them as targets on your chartplotter. RYA guidance.
In practice: you can see a cargo ship 15 miles away, see it is doing 18 knots on a course that will cross yours in 23 minutes, and alter course now — all before it is even visible to the naked eye. In poor visibility or busy shipping lanes, that is invaluable.
Is AIS Legally Required?
For commercial vessels of 300 gross tons and above on international voyages — yes, under SOLAS V. For recreational vessels — no legal requirement in UK waters.
But this sits in the same category as lifejackets and EPIRBs — equipment you should have regardless. The cost has dropped significantly and the safety benefit is substantial, particularly for overnight passages and sailing near busy shipping lanes.
Class A vs Class B vs Receive-Only
Class A — mandatory for large commercial vessels. 12.5 watts, updates every 2 to 10 seconds. Not relevant for recreational boats.
Class B — designed for recreational and smaller commercial vessels. 2 watts, updates every 30 seconds. Transmits and receives. This is what most recreational sailors need.
Class B+ SOTDMA — newer standard, 5 watts, faster updates, better in busy traffic areas. Worth considering for offshore passages.
Receive-only — you can see other vessels but they cannot see you. Cheaper but a significant limitation. Commercial vessels will not know you are there. Not recommended as your only AIS solution.
A Practical Point on Range
AIS is line-of-sight, like a VHF— range depends on antenna height. A Class B unit gives roughly 5 to 6 nautical miles surface-to-surface. Mount the antenna as high as possible. Aircraft can detect AIS signals from much greater distances. See the SOLAS V Requirements.
Our Recommended AIS Units
Digital Yacht iAISTX Class B AIS Transponder
The all in one and only one we can recommend on Amazon: iAISTX is a Class B AIS transponder with Wi-Fi interface designed specifically for the growing number of boaters who use a tablet for their navigation tasks
FAQs
Can other people track my boat online using AIS?
Yes — sites like MarineTraffic.com aggregate AIS data publicly. Useful for family to follow your passage. You can switch AIS off temporarily for privacy but this makes you invisible to commercial traffic.
Does AIS replace radar?
No. Radar detects objects independently including vessels without AIS and channel markers. AIS complements radar — use both where possible.
Do I need a licence?
Your vessel needs a Ship Radio Licence covering AIS as part of your onboard radio equipment. Your MMSI number comes from this registration. Register at ofcom.org.uk in the UK.
AIS carriage requirements are governed by SOLAS V. Verify current requirements for your vessel at gov.uk/mca.
The information in this article is for general guidance only and does not constitute professional safety advice. Always consult current MCA, SOLAS, and HSE official documentation and a qualified marine safety professional before making any safety-critical decisions. Product specifications and regulatory requirements change — always verify against current official sources before purchase. Where affiliate links appear on this site, they are clearly disclosed and never influence our recommendations. marinesafetyguide.com participates in affiliate programmes including Amazon Associates and the Awin network and may earn a small commission on purchases made through links on this site, at no extra cost to you.
