Marine sensing, explained

Marine sensing: the short version

Marine environments are unforgiving places to measure anything. Salt, spray, vibration, temperature swings, restricted access and constantly changing conditions all place demands on sensing equipment.

At the same time, the data those sensors produce has a direct bearing on vessel safety, positioning, navigation, operational efficiency and maintenance decisions. A wind reading feeds a dynamic positioning controller. A tank level informs a bunkering decision. An oil debris trend changes when a gearbox comes out.

Gill provides marine sensing technologies for measuring wind and weather, equipment position, fluid levels and machinery condition. The portfolio includes solid-state ultrasonic wind sensors, integrated marine weather stations, non-contact position and level sensors, and oil debris monitoring technology.

The approach is straightforward: provide reliable measurements, minimise unnecessary mechanical complexity, and make the resulting data easy to integrate into the systems that depend on it.

This guide answers the technical and application questions that come up most often in marine specification calls, from choosing an ultrasonic wind sensor and integrating weather data with dynamic positioning, through to calibration, certification, level sensing and machinery condition monitoring. It is written for naval architects, marine and offshore engineers, system integrators and vessel operators who are specifying equipment rather than buying a catalogue number.

Wind and weather sensing

What wind sensors do ships use?

Ships use a range of wind sensors depending on the vessel, the application and the measurement performance required. Ultrasonic wind sensors are widely used where reliable wind speed and direction, low maintenance and robust operation matter.

Gill’s ultrasonic wind sensors are used across marine applications including vessel navigation, dynamic positioning, offshore operations, ports and harbours, and environmental monitoring. A dedicated wind sensor suits installations where wind speed and direction are the primary measurements. An integrated weather station provides a wider set of meteorological parameters from a single instrument and a single cable run.

Which sensor suits depends on accuracy, environmental conditions, certification, mounting location, communications and integration with the vessel’s wider systems. Those six factors, in that order, usually settle the decision.

How do ultrasonic anemometers work?

Ultrasonic anemometers measure wind speed and direction using sound waves rather than mechanical components. The sensor measures how the movement of air affects ultrasonic signals travelling between transducers, and calculates wind speed and direction from the difference.

Because the measurement principle does not rely on cups, vanes or bearings, ultrasonic anemometers avoid the mechanical wear associated with conventional wind sensors. There is no starting threshold to overcome and no inertia to settle, so response is fast and light winds are resolved as well as strong ones.

That makes the technology well suited to marine and offshore applications where continuous operation, reliability and reduced maintenance are important.

What are the benefits of ultrasonic wind sensing?

Ultrasonic wind sensing provides wind speed and direction without mechanical moving parts.

For marine applications, removing moving components reduces mechanical wear and maintenance while supporting reliable operation in exposed positions. Gill ultrasonic sensors can also incorporate capabilities such as GPS and electronic compass functionality, depending on the product.

On vessels and offshore structures where equipment is difficult or expensive to reach, reducing mechanical failure points contributes to greater availability and lower lifetime ownership cost. The commercial case is rarely the purchase price. It is the cost of the access.

How do you choose a marine wind sensor?

Choosing a marine wind sensor starts with the application, not with the highest specification on the datasheet.

The considerations that matter are the wind speed and direction accuracy required, the operating environment, the vessel type, the mounting location, environmental protection, marine or hazardous-area certification, communication requirements, and integration with navigation, monitoring or dynamic positioning systems.

The application may also determine whether a dedicated wind sensor or a multi-parameter weather station is the better choice. Gill’s marine portfolio includes several ultrasonic sensing technologies so the solution can be matched to the vessel or installation rather than the other way round.

How accurate are ultrasonic anemometers?

The accuracy of an ultrasonic anemometer depends on the specific sensor, its measurement range, environmental conditions, installation and application. Across the Gill 2-axis range, a typical published figure is around two per cent of reading at 12 m/s for wind speed and around two degrees for direction, with performance stated per product.

Correct installation matters as much as the instrument. Structures, masts, funnels and other equipment disturb airflow and introduce errors that no sensor specification can recover. A well-sited average sensor will out-measure a badly sited excellent one.

Where measurement accuracy is critical, calibration and appropriate verification should form part of the overall sensing strategy rather than being treated as a one-off at handover.

How often should marine wind sensors be calibrated?

The appropriate calibration interval depends on the sensor, the application, the operating environment and the level of measurement assurance required.

Marine environments expose equipment to salt, moisture, temperature variation and other environmental stresses. A planned calibration programme is therefore important where accurate measurements support safety, operational decisions, research or regulatory requirements.

There is no single interval that applies to every marine installation. Set it against the sensor, the application, the relevant standards and your own assurance requirements. In practice, routine verification against a known reference is often more valuable than frequent recalibration, because it catches drift and installation problems between calibrations.

How are wind sensors mounted on ships?

Marine wind sensors should be mounted where they have representative exposure to airflow, with the least possible interference from the vessel’s structure, masts and other equipment.

Mounting position, height, orientation and proximity to obstructions all influence the measurement. Gill’s MaxiMet Marine installation guidance, for example, recommends positioning the sensor clear of structures that could obstruct airflow or create turbulence, with the arrangement determined by the installation.

The correct approach depends on the vessel, the sensor and the application. Consider the airflow around the complete structure rather than treating the sensor as an isolated component, and record the alignment offset used at commissioning. Heading errors introduced at installation are one of the most common causes of a true wind calculation that nobody trusts.

What weather instruments are used offshore?

Offshore weather monitoring usually combines wind speed and direction with air temperature, relative humidity, atmospheric pressure and, depending on the site, other meteorological measurements.

Gill’s compact weather stations combine several environmental measurements in a single instrument, while dedicated ultrasonic wind sensors are used where wind is the primary requirement.

Applications include offshore platforms, offshore wind farms, marine research, buoys, helidecks, vessels and environmental monitoring. The appropriate instrumentation depends on the measurements required and the conditions the equipment has to survive.

How do ships measure weather?

Ships measure weather using onboard meteorological sensors that collect real-time information about conditions around the vessel.

Depending on the application, measurements can include wind speed and direction, temperature, humidity and atmospheric pressure. That data is then supplied to navigation, monitoring, weather display and control systems.

Gill’s ultrasonic wind sensors and MaxiMet Marine weather stations provide compact sensing for applications where reliable local environmental data is required. MaxiMet Marine combines wind, temperature, humidity and pressure measurement with compass information, and GPS as an option, in a single instrument and a single output string.

What weather stations do ships use?

Ships use compact marine weather stations where several meteorological measurements are needed from one instrument and one cable run.

MaxiMet Marine GMX260 and GMX560 are the two marine models in the MaxiMet range. GMX560 measures wind alongside temperature, humidity and pressure; GMX260 measures wind. Both carry a six-axis compass, which is what makes them suitable for a moving platform, and both are rated to IP66 and IP68. GPS is optional on both, and heating is available on GMX560.

For applications concerned primarily with wind speed and direction, or where a formal marine wind approval is required, a dedicated ultrasonic wind sensor is usually the better answer than a compact station.

What sensors are required on helidecks?

Helideck monitoring requirements depend on the installation, the vessel and the applicable aviation and marine requirements. CAP 437 is the reference most UK and North Sea operators work to.

Weather sensing is central to most helideck monitoring systems, with wind speed and direction describing conditions at the landing area. Additional environmental measurements may be required depending on the system and the operational requirements.

Gill’s marine weather sensing technology is designed for applications where accurate, reliable environmental data is needed in exposed positions. Select against the specific certification, installation and operational requirements of the helideck rather than against a generic specification.

Can weather sensors integrate with dynamic positioning systems?

Yes. Marine weather sensors can supply wind speed and direction directly to dynamic positioning systems.

Wind is one of the environmental forces acting on a vessel’s position and heading. A DP system uses information from onboard sensors, wind sensors among them, to calculate the thrust required to hold station. Wind data is a feed-forward input, which is why its quality and its update rate both matter: the controller acts on it before the vessel has moved.

Gill’s WindObserver range is used in dynamic positioning applications, with marine type approval available for relevant products. Select against the DP architecture, the accuracy requirement, the environmental conditions and the applicable certification. Redundancy is usually specified at sensor level as well as at controller level.

Offshore and remote monitoring

How are buoys monitored?

Environmental monitoring buoys combine weather sensors with other instrumentation and a data communications link to collect information from remote locations.

Gill weather stations can be integrated into buoy-based monitoring systems to measure local meteorological conditions alongside other environmental parameters, giving a more complete picture of conditions at the monitoring location.

Buoys are used for environmental research, coastal monitoring, offshore observation and marine data collection, where reliable sensing is required despite constant exposure to weather and sea state. On a buoy the real cost is rarely the instrument. It is the vessel time needed to reach it, which is why low-maintenance sensing pays for itself quickly.

What sensors do offshore platforms use?

Offshore platforms use a combination of environmental, weather, position, level and machinery monitoring sensors depending on their operational requirements.

Weather sensors provide wind and meteorological data. Position and level sensing monitors equipment and tanks. Machinery condition monitoring gives early warning of developing wear.

Gill’s marine sensing portfolio can therefore contribute to several monitoring requirements on a single installation, with individual sensors selected against the application, operating conditions and system architecture. Where the location is a classified hazardous area, the certification requirement usually narrows the choice before anything else does.

What sensors are used on autonomous and uncrewed vessels?

Autonomous and uncrewed surface vessels use sensors to measure environmental conditions, vessel position and onboard equipment status.

Gill’s marine portfolio includes ultrasonic wind and weather sensors alongside compact weather stations and solid-state level sensing. For autonomous platforms, low power consumption, compact size, robust construction and reliable data all carry more weight than they would on a crewed vessel.

WindUltra is the example that makes the point: 270 g with its pole mount, less than 100 mW without heating in calm conditions, and rated to IP66, IP68 and IP69k, so submersion is a survivable event rather than a failure. LevelLite and LevelPro use solid-state capacitive sensing with no moving parts, which suits monitoring fuel and fluid levels where that information informs mission planning and endurance.

An uncrewed platform cannot diagnose its own instruments. Whatever is fitted has to be right for the whole deployment, not just the first week of it.

Position, level and machinery

What position sensors are used on ships?

Marine position sensors monitor the position of equipment including rudders, thrusters, hatches, ramps, davits and cranes.

Gill’s Blade non-contact position sensing technology provides position feedback without mechanical contact or linkage between the sensor and the equipment being monitored. The sensor and its target are two separate parts with nothing touching, so there is nothing to wear out.

The result is reliable position measurement without the mechanical components that wear, need adjustment or add to the maintenance schedule.

What are the benefits of non-contact position sensing?

Non-contact position sensing removes mechanical contact between the sensor and the equipment being measured.

That eliminates linkages that wear over time, which reduces maintenance while still providing reliable position feedback. It is particularly valuable on marine equipment operating in demanding conditions or in positions where access for maintenance is difficult, expensive or only possible in dock.

Removing wear points also contributes to longer service life and lower lifetime ownership costs. The Blade sensors are rated to IP67 and sealed for temporary immersion (1 m for 30 min), with configurable measurement ranges and both analogue and digital outputs depending on the model.

What level sensors are used in marine applications?

Marine level sensors monitor the level of fluids in tanks and other onboard systems. Typical applications include fuel, ballast, bilge and catch tanks.

Gill’s LevelPro and LevelLite use solid-state capacitive sensing with no floats and no moving parts. LevelPro is the robust general-purpose sensor, in corrosion-resistant stainless steel with fully sealed electronics, rated to IP66 and IP68. LevelLite is the lightweight aluminium version for weight-critical platforms, rated to IP68, with voltage and current outputs, RS232 for configuration and CAN on bespoke sensors.

The right technology depends on the fluid, the tank configuration, the accuracy required and the operating environment. Conductive, dirty, viscous or corrosive liquids are a different problem and are handled by a different sensor in the range.

How are fuel and ballast levels measured on ships?

Fuel and ballast levels can be monitored using non-contact level sensing technology.

Gill’s solid-state level sensors measure tank contents without relying on mechanical floats or other moving components inside the tank. Fewer mechanical components exposed to the tank environment means less to inspect, less to seize and less to replace.

The right sensing technology depends on the tank configuration, the fluid characteristics, the measurement requirement and the wider vessel system. Tank geometry is usually the constraint that decides it.

What rotary sensors are used in marine engines?

Rotary sensing monitors the position, speed or movement of rotating components within marine machinery.

The right technology depends on the equipment, the measurement required and the operating environment. Applications include rotating machinery where reliable feedback is needed for control, instrumentation or condition monitoring. Gill’s Blade360 sensor covers a full 360 degrees with a configurable range and no mechanical contact.

Select against the specific machinery, measurement and integration requirement rather than treating rotary sensing as a single application category. The requirements for a control loop and for a condition monitoring trend are not the same.

What is oil debris monitoring used for in marine engines?

Oil debris monitoring identifies signs of developing mechanical wear inside machinery, before that wear becomes a failure.

Gill’s WearDetect technology monitors ferrous wear debris in lubricating oil, distinguishing fine particles from coarse ones. It also monitors water presence and oil temperature. It fits as a smart replacement for a sump plug, or into an oil bypass circuit, and outputs over analogue, CANbus or Modbus RTU.

Monitoring those characteristics gives an indication of developing wear between planned overhauls, which helps operators make better-informed decisions about machinery condition and maintenance timing.

How can oil debris sensors help identify machinery wear?

As machinery components wear, particles enter the lubricating oil. Monitoring those particles indicates that wear is developing and, from the fine-to-coarse ratio, gives a sense of how quickly.

WearDetect captures ferrous debris on a magnet and reports how much has been collected, separating fine particles from coarse. It also monitors water presence and oil temperature, both of which affect the condition of the oil itself.

This adds information about machinery condition between planned overhauls and supports a more informed approach to maintenance, helping operators identify potential problems before they develop into significant ones. It complements oil sampling and vibration monitoring rather than replacing either.

Calibration and certification

Why calibrate marine sensors?

Calibration verifies that a sensor continues to measure within its specified performance.

Where environmental data informs navigation, operational decisions, safety, research or regulatory compliance, confidence in the measurement matters. Calibration identifies drift and provides documented evidence that the sensor still performs as expected.

The right approach and interval depend on the sensor, the application, the operating environment and the relevant customer or regulatory requirements. Calibration cannot correct an installation problem, so treat siting and alignment as the first line of measurement assurance and calibration as the second.

What is UKAS calibration?

UKAS calibration is calibration performed by a laboratory accredited by the United Kingdom Accreditation Service to the relevant international standard.

UKAS accreditation gives confidence that the laboratory operates to defined requirements for technical competence, impartiality and consistent calibration practice, and that its results are traceable to national standards.

For marine and environmental sensing where traceability and measurement assurance matter, accredited calibration provides additional confidence in the validity of the results, and a certificate that stands up when someone asks for it.

What does ATEX mean?

ATEX refers to the European requirements covering equipment and protective systems intended for use in potentially explosive atmospheres. The name comes from ATmospheres EXplosibles.

ATEX requirements apply where an explosive atmosphere may be present because of gases, vapours, mists or dusts. Offshore oil and gas installations are the most common marine context.

Where marine or offshore equipment is destined for a potentially hazardous area, the applicable certification requirement should be settled as part of the overall system design, not discovered at commissioning.

What is IECEx certification?

IECEx is the international certification system covering equipment and services intended for use in explosive atmospheres.

It provides an internationally recognised framework for demonstrating that equipment meets the applicable standards for hazardous environments, which simplifies specification across jurisdictions.

Gill’s WindObserver IS is the intrinsically safe variant in the range, certified to IECEx, ATEX and UKEX for hazardous-area applications. It is not a drop-in replacement for a standard WindObserver, so treat it as a separate specification decision rather than an option box.

What certifications are available for Gill marine sensors?

Certification is held at product and variant level, not at range level, so it needs checking per model rather than assumed across a family.

• WindObserver II holds Lloyd’s Register Type Approval and an ABS Product Design Assessment for marine and offshore applications.
• WindObserver IS holds ATEX, IECEx and UKEX certification for hazardous areas, and meets EN 60945:2002 for EMC. It does not carry the marine type approvals.
• WindObserver 70 is the model referenced for airport and AWOS use, with the relevant CAA and FAA acceptance.
• MaxiMet Marine GMX260 and GMX560 are built for marine environments and rated to IP66 and IP68.
• WindUltra is tested to BS EN 60945 and rated to IP66, IP68 and IP69k.

Consider certification alongside the vessel, the installation environment, the operating requirement and the applicable regulations. If an approval is a shortlist condition, confirm it against the current certificate for the exact model before it goes into a specification.

Integration and connectivity

Can marine sensors output NMEA?

Yes. Applicable Gill marine sensors provide data using NMEA 0183, so measurements can be taken into marine navigation, monitoring and control systems without a translation layer.

NMEA is widely used across marine electronics, which makes it the default interface where sensor data has to be shared with existing vessel equipment. Gill sensors also support other interfaces depending on the product, including RS232, RS422, RS485 and Modbus.

Check the available outputs against the requirements of the receiving system when specifying, and confirm the sentence format as well as the physical layer. Two devices can both be NMEA 0183 and still not talk to each other.

What communication protocols do marine sensors support?

Gill marine sensors support a range of established interfaces and protocols, including NMEA 0183, RS232, RS422, RS485 and Modbus RTU, depending on the product. Analogue outputs and SDI-12 are available on some models, and WindUltra adds USB.

That means sensor data can be taken into navigation, monitoring, control and data acquisition systems without every installation needing a proprietary communications architecture.

Available interfaces vary by product, so select the sensor against the requirements of the wider vessel system rather than fitting the system around the sensor.

Can marine sensors integrate with existing vessel systems?

Yes. Gill marine sensors are designed to integrate with wider vessel monitoring, navigation and control systems using established communication interfaces.

Depending on the product, those interfaces include NMEA 0183, RS232, RS422, RS485 and Modbus. Sensor data becomes part of an existing system architecture rather than sitting as a standalone measurement on its own display.

Application-specific integration is also supported where standard configurations do not fully meet the requirements of a particular marine system. Where a sensor has to feed several consumers at once, a bridge display, a DP controller, a data logger and a fleet reporting platform, plan the communications architecture before the sensor is chosen.

Choosing the right marine sensing technology

There is no single sensor that is right for every marine application.

The right choice depends on what needs to be measured, where the sensor will operate, how the data will be used and what the wider system requires. Environmental exposure, certification, maintenance access, communication protocols, accuracy and lifetime ownership cost all pull the decision in different directions.

Gill’s marine sensing portfolio is built to cover those different requirements, from dedicated ultrasonic wind measurement and integrated weather monitoring through to non-contact position and level sensing and machinery condition monitoring.

If you know the measurement you need but are not sure which sensing technology or configuration is appropriate, that is a conversation worth having early. Specification changes are cheap on a drawing and expensive on a vessel.