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Cerulean ROVL Mk II : 300 meters depth rated and Autosync

This week we launched the most cost-effective position system in the market with a 300-meter depth rating and no need to calibrate crystal oscillators or manually sync the distance between units at mission start-up; you can get up and running in no time.

The ROV Locator Mark II includes a transmitter mounted on the ROV and a receiver module located on the surface. Simply power up, start the dive and track the ROV location in real-time on the QGroundControl map display. Serial communication and API are available.

Autosync works by exposing the Receiver and Transmitter to GPS or GNSS signals at the start of the mission and optionally at intervals during the mission. Satellite acquisition occurs typically within 30 seconds of power-up. In the canonical case of a ROVL receiver sited near the ROV operator and a ROVL transmitter on the ROV, the satellite acquisition will typically occur in the background, and at the time the ROV is being readied for launch and while the ROVL Receiver IMU calibration is being done.

If you want to know what we mean by “cost-effective” – Go ahead and take a peek :wink:

Cerulean ROV Locator Mk II


Exciting stuff! :smiley:

Always cool to see products that can improve the status quo, and positioning is definitely a big one for marine robotics. Keen to see where this goes :slight_smile:

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Dennys they look really good. We’ve been happy with the unit we bought at Blue Robotics open house, but I think it’s time for a second system. The Autosync would eliminate the only step unfamiliar to most operators and I think these will be a big hit.

@dennysb Looks great. Does it block the Ping360 sonar on the ROV?

Their website specs say it uses a ping frequency of 25kHz, whereas the Ping360 uses 750kHz, so there shouldn’t be any particular sonar noise issues :slight_smile:

Of course sonar things like to be stuck out, so if they’re physically in each other’s way then they can still block scanning/locating in a particular direction.

Yes, I was talking about it physically blocking the Ping360 and making a blind spot to the side. I wasn’t sure if it would be really annoying, or barely even noticeable.

That’s probably largely dependent on use-case and how you install it. The further apart they are the less they’ll block each other, and given the large vertical beamwidth of the Ping360 tall obstacles aren’t likely to be particularly effected, although nearby small obstacles would be harder to detect (the maths to determine the affected region shouldn’t be too complicated). From a locating perspective the biggest issues would be at/near the surface where the receiver isn’t very far above the transmitter so the sideways direction matters more. Perhaps @dennysb has some further insight :slight_smile:

It’s also possible to mount the ping360 on the bottom of the ROV, although that might then introduce the risk of scraping or damaging it when the ROV is at the sea floor, depending on mounting method.

No issues with the Ping 360 and our ROVL family – I fact that is a common set-up in many of our customers configurations.


Here you see the Ping360 and a ROVL Mk I coexisting on a Poseidon Robotics (@Peter_Schubert ). The Mark II has a different mounting system – but you get the picture.


I attached the ROVL transmitter to the buoyancy block way at the aft of the ROV. No issues at all.

Hi,What is the principle of his underwater positioning? I didn’t understand

My apologies in advance If I misunderstand your question.

This system is designed for low-cost, medium-accuracy localization of underwater objects.

• The system can be used to guide an ROV to an area of interest, either manually or autonomously

• The system can be used to locate an ROV

• Other applications are also possible

This system is designed and priced for use by people who need to know generally where their ROV is located. It is not intended to be a survey-grade instrument, and it has few features not directly required for the primary function.

A complete system requires both a transmitter and a receiver. For systems without autosync, receivers are paired to specific transmitters via clock calibration and should not be interchanged. Multiple receivers can be paired with a single transmitter. For systems with autosync, all receivers and transmitters are interoperable and require no clock calibration.

The system works by syncing the clocks of a transmitter and receiver, either at the start of each mission for non-autosync versions or automatically via GPS for autosync versions. The transmitter sends a sound pulse once per second. The receiver uses time-of-flight to calculate slant range to the transmitter and signal phase measurements to determine the arrival angle of the sound pulse.

Slant range error accumulation, baseline (typical) 2 m/hr

Slant range error accumulation, baseline (autosync) 0.5 m/hr

Adding to dennys’ response, the ROVL Mk II product page links to a user guide. It provides an example setup as below - the relevant maths and parameter descriptions are on page 45.

Note that because the positioning is based on measuring the incoming sound to determine the horizontal direction, and time of flight for the distance, reflections from nearby objects can cause spurious/incorrect readings. There’s some more detail about that on page 25 of their user guide.

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That’s great! SO is it an ultra short baseline product?

Thanks Eliot!Thank you for every answer!

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From the Wikipedia page on Underwater acoustic positioning systems, yes:

Cerulean ROVL is a slightly different from a traditional USBL.

The ROVL is very similar to a USBL. The main difference is that USBL systems usually have bi-directional pinging. We have unidirectional pinging. Bi-directional pinging allows a USBL system to determine slant range with no outside assistance. Our system needs either a GPS clock (ROVL autosync versions) or a user initialization input (baseline systems) to determine slant range.

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