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The Mark III ROV Locator takes the ease of use of a cost-effective underwater positioning solution to a new level. Using the interrogate/response model of a traditional USBL system, it dispenses with both distance sync at the start of the mission and period crystal calibration procedures. With the supplied topside CeruleanTracker software, you can get up and running in no time or use the open API to integrate the Mk III with your own software. The MK III has a 300-meter depth rating, and with no timebase drift, the system can remain submerged indefinitely without losing slant range accuracy.

Product Choices

Product delivery lead time is TBD

HS Code: 9015.80

Max Depth: 300 meters

Ping freq.: 25 kHz

Max Range: 500 meters

Update rate: 1 Hz


The Mark III, ROV Locator bundle includes a transponder (usually mounted on the ROV or AUV) and a transceiver module (usually located on the surface). It also comes with a mounting ring and adapter for your ROV or AUV. ROV/AUV integration can be as simple as just supplying power from the vehicle battery. You can also add a dedicated battery for the Mark III to track the vehicle in case of primary battery failure. Simply apply power, start the dive and track the ROV location in real-time on a QGroundControl map display or use the free CeruleanMap display software if you don't want to use QGC. Serial communication to either transceiver or transponder is available, and the open API is documented in the user manual.

In operation, the Mark III transceiver sends an interrogation sonar pulse to the transponder, which returns a sonar reply. The slant range is calculated from the round-trip time of flight. Unlike the Mark II systems, start-of-mission timebase synchronization is never needed. The Mark III system can remain submerged indefinitely without fear of slant range accuracy drift. Only one Mark III pair can operate in an area at one time.

Download Resources

Software Release (2022-11-04)

ROV Locator Manual

Cerulean Tracker Manual

BlueROV Installation

CAD Models


Maximum Depth Exposure (minimum crush depth)


Volume, Transceiver Unit

480 ml

Mass, Transceiver Unit

600 gm

Volume, Transponder Unit

300 ml

Mass, Transponder Unit

410 gm

Absolute Maximum Range

500 m

Typical Usable Range

300 m

Apparent Yaw/Azimuth resolution


Apparent Elevation angle resolution


Slant range measurement resolution

0.1 m

IMU Euler angle accuracy, typical (magnetic errors not included)

Update rate

1 Hz

Transceiver Ping Frequency

43 kHz

Transponder Ping Frequency

25 kHz

Transceiver V-in power (See note)

Vin: 5-16 V DC
2.5W average, 3.5W peak @5V DC
2.1W average, 3.3W peak @12V DC

Transponder V-in power (See note)

Vin: 5-28 V DC
1.7W average 2.9W peak @5V DC
1.3W average, 4.1W peak @16V DC

Serial Comms Voltage Levels

3.3V TTL or 5V TTL, auto sense

NOTE : Power supplies for both units must be able to supply burst currents to prevent drop-out and erratic operation. While the transmitter will work with a low impedance 5V supply we recommend using 9V or higher, unless you know how to figure out if your 5V power supply is low-enough impedance.

NOTE : Resolution does not equal accuracy.