Marine Speed Log Regulation According to SOLAS Chapter V: What Every Vessel Operator Needs to Know

Marine Speed Log Regulation According to SOLAS Chapter V: What Every Vessel Operator Needs to Know

There is a piece of equipment on the bridge that most people overlook until something goes wrong. The speed log. It sits there, quietly displaying knots and nautical miles, while the captain watches the radar and the ECDIS and the AIS. But when the port state control officer steps aboard and asks to see the type approval certificate, suddenly everyone remembers just how seriously SOLAS takes this little box.

We design and manufacture our own navigation and communication equipment from the transducer up. Speed logs, echo sounders, AIS, the whole stack. And over the years, we have watched too many vessel operators discover too late that their "compliant" speed log was never actually compliant at all.

The Legal Foundation: SOLAS Chapter V, Regulation 19

The carriage requirements for speed and distance measuring equipment live in SOLAS Chapter V, Regulation 19. This is the regulation that tells you what navigational equipment your ship must carry, based on ship type and tonnage.

For speed logs, the requirement breaks down into two distinct categories.

First, SOLAS regulation V/19.2.3.4 requires that all cargo ships of 300 gross tonnage and above, and all passenger ships regardless of size, must be fitted with a speed and distance measuring device capable of measuring speed and distance through the water. This is the baseline requirement. If your vessel meets that tonnage threshold and operates on international voyages, you need a speed log that measures speed through water (STW).

Second, for ships of 50,000 gross tonnage and above, the requirements get stricter. Regulation V/19.2.9.2 requires these vessels to carry an additional device capable of measuring speed over the ground in both the forward and athwartships (sideways) direction.

The 2014 Amendment That Changed Everything

Here is where many operators get caught out. In 2012, the IMO Maritime Safety Committee adopted resolution MSC.334(90), which amended the performance standards for speed and distance measuring devices. These amendments apply to devices installed on ships constructed on or after 1 July 2014.

The critical change? For ships of 50,000 GT and above that require both types of speed measurement, the requirement must be fulfilled by two separate devices. Not one device that does both. Two physically separate units. One that measures speed through water. A separate one that measures speed over the ground in forward and athwartships directions.

This clarification came through IMO circular MSC.1/Circ.1429. And it matters because some manufacturers were marketing single devices that claimed to do both. Under the new rules, that does not fly.

The Performance Standards Behind the Requirement

Carriage is one thing. Performance is another. SOLAS Regulation 18 requires that all installed navigation equipment must be type-approved in accordance with relevant IMO performance standards.

For speed logs, the key performance standards are IMO Resolution A.824(19) and its amendments through MSC.334(90). These resolutions set the technical floor for what a compliant speed log must deliver.

The accuracy requirements are specific. Speed must be accurate within 2 percent of the vessel's speed or 0.2 knots, whichever is greater. Distance measurements must remain within 2 percent of the distance run in one hour or 0.2 nautical miles, whichever is greater.

Display requirements are equally detailed. Digital speed displays must read in increments no greater than 0.1 knots. Distance readings must cover at least 0 to 9999.9 nautical miles with 0.1-mile increments. All displays must remain readable in both day and night conditions.

The equipment must also perform reliably under real-world conditions. That means functioning properly when the ship rolls up to ±10 degrees and pitches up to ±5 degrees. It must work in waters at least three meters deep below the keel.

The IEC Standards That Back It All Up

Behind the IMO resolutions sits IEC 61023, the international standard that specifies the minimum performance requirements, methods of testing, and required test results for marine speed and distance measuring equipment (SDME). This standard works in conjunction with IEC 60945, the general requirements for marine equipment.

When a manufacturer claims their speed log is SOLAS-compliant, they should be able to point to type approval testing that meets these IEC standards. Not just a self-declaration. Actual testing by a recognized notified body.

The Practical Reality of Compliance

Here is what all of this means in practice. If you are operating a cargo ship above 300 GT on international voyages, you need a speed log that measures speed through water. That unit must meet the accuracy requirements. It must pass the environmental tests. It must carry type approval from a recognized classification society.

If your ship is 50,000 GT or above and was constructed after 1 July 2014, you need two separate devices. One for STW. One for SOG with athwartship capability. Both must be type-approved. Both must meet the performance standards.

And if your speed log malfunctions? Recognized organizations are authorized to issue temporary exemptions, but these are typically limited to six months and require repair at the earliest opportunity. You cannot simply sail without a working speed log indefinitely.

What This Means for Equipment Selection

When you are choosing a speed log for your vessel, or when you are evaluating a manufacturer as a potential supplier, there are specific questions you should ask.

First, ask for the type approval certificate. Not a brochure. Not a marketing claim. The actual certificate from a recognized classification society.

Second, ask which IMO resolutions the equipment complies with. If they cannot reference A.824(19) and MSC.334(90) where applicable, keep looking.

Third, ask about the IEC standards. IEC 61023 is the technical backbone. If the manufacturer does not know what that is, they are not serious about compliance.

Fourth, for vessels above 50,000 GT, ask specifically how the STW and SOG functions are delivered. If they point to a single device that claims to do both, ask how that squares with MSC.1/Circ.1429.

Why We Build Our Own

When we build a speed log, we know exactly what went into it. We know which tests it passed and which it barely scraped through. We know because we run the same tests in our own lab before we ever send a unit to a notified body.

SOLAS Chapter V is not a suggestion. It is not a marketing checkbox. It is the legal framework that keeps vessels safe and crews alive. The speed log is a small piece of that framework, but it is a critical one. Without accurate speed data, collision avoidance degrades. Voyage planning becomes guesswork. Grounding risk increases.