USBL Type Underwater Position Measurement


Tracks the Positions of Underwater Structures, Devices and Divers in Real Time

Checking on underwater situations from onboard a ship or on land, and controlling operations there, is not easy. In site environments where there is a chance of losing equipment, or divers being involved in accidents, underwater measurement data is indispensable for the safe performance of work and surveys. This TrackLink USBL system is the most practical, compact, light, and reasonable system for obtaining position data of underwater devices and divers.

The light, compact USBL (Ultra Short Base Line) type underwater position measurement device uses broadband, acoustic, spread and spectrum signal processing methods to detect distance, reducing false readings.

System Configuration

(*Click to enlarge)


USBL determines distance to the transponder by the time it takes the sound waves to travel there and back, and the speed of the sound through the water. Angles are determined by the phase differences in the USBL wave reception array (an array of multiple received wave elements), and the relative position of the transponder in three-dimensional space with respect to the transceiver can be determined. Also, by adding the transponder’s relative position to the transceiver’s terrestrial co-ordinates (latitude and longitude) and attitude angle (inclination from the horizontal and orientation), the transponder’s latitude and longitude can be obtained.


  • Few false readings even in site environments where the noise level is high.
  • Allows data transmission between the transponder and onboard apparatus.
  • Select according to distance and precision and precision to match with installed equipment.
  • Compact, light, easy to connect


  • Remotely operated vehicles (ROV), autonomous underwater vehicles (AUV), target objects and ship position shown in terrestrial co-ordinates.
  • Position display of underwater moored objects and ship, and acquisition of mooring data.
  • Position recording and display of towed bodies in terrestrial co-ordinates (Side scan sonar).

Positioning When Installing Sunken Reefs


The transponder is fitted to a suspended frame or wire to secure positioning during installation. By fitting two transponders, the reef’s orientation can also be managed.

ROV/AUV Position Management


Devices can be fitted to ROVs and AUVs for position management. Can also be used for surveys of seabed cable routes.

Transceiver and Transponder

The transponder is selected from among models compatible with the transceiver’s frequency, in accordance with the transmission distance.
(Example: If communicating with a TrackLink1500 transceiver at a distance of 1,000m, a TN1510 would be selected.)
Either built-in battery models or external power supply models can be chosen in accordance with the intended use. They can also be operated by remote control (sound source component extension type).


Example of Use in the Setting of Wave Dissipating Blocks for a Breakwater


An example of the use of the USBL type underwater position measuring device is the determination system for laying covering blocks and asphalt mats in installing breakwater wave dissipating blocks.
The laying of covering blocks and asphalt mats in front of the wave dissipating blocks is effective in preventing coastal erosion and the undermining of sea walls. When a crane on a crane barge is laying objects underwater, surges in the water can cause the objects to oscillate, preventing accurate positioning. In addition, sand from the bottom caused to swirl up by the surges can adversely affect the safety of divers. As a result, there is a need for a system which can accurately determine the positions of objects being placed underwater, and divers.
We have developed a system using highly accurate transponders and an RTK-GNSS to display the positions of divers and objects to be placed, in both plan and cross-sectional views.

Case Study ⇒Safe and Accurate Installation of Structures Underwater