Topside Navigation Pod - Usbl


The FUSION out of the box has a variety of navigational sensors that enable accurate positioning in most situations.  An optional Topside Navigation Pod (TSNP) system is available to provide additional capability in deeper water or longer missions or as an acoustic communication system.  Like all SRS products the TSNP is an innovative and welcome approach to USBL design.


Ultra Short Baseline - Usbl

Traditionally USBL systems are a variety of components put together by operators to provide underwater navigation to ROV systems.  Operators have to mount the USBL, setup a GNSS and key to the USBL, run USBL software and all in a small footprint.  Often times the result is poor performance.  The TSNP resolves all common issues by building all into a standalone battery powered unit and simply needs to be turned on and put in the water.

The TSNP builds on the impressive SeaTrac X150 USBL head that is mounted to a keyed coupler with pass through to internal electronics, high end AHRS, GNSS and battery.  There is no requirement to connect to any external computers or the HMI to operate, simply power on and everything is taken care of.  The unique design is waterproof and supplied with a float so that the unit can be placed in the water away from the noisy operating platform.

Use of the TSNP provides real world corrections to potential error in navigation.   It works by interrogating the FUSION and based on time, bearing and the fact the TSNP knows where it is can calculate the FUSION position.  Once calculated the position is acoustically sent to FUSION so that the system can operate in AUV, Diver and ROV mode where a tether might not be used.

Key Specifications:

  • Range: ~1,000m (3,280ft)
  • Range Resolution: ~0.1m (4in)
  • Angular Resolution: ~1 degree


The TSNP system is more than a USBL tracking system for the FUSION in ROV mode.  Since the SeaTrac USBL head is also a modem the TSNP can be used as an acoustic communicator between the HMI and FUSION with any requirement for tether. 

AUV Mode
When operating FUSION in AUV mode and conducting missions the TSNP not only tracks FUSION’s position, but also provides the operator with a method to send commands.  A simple panel in the user interface allows the operator to send commands such as abort and change mission.

With divers operating FUSION vehicles topside operators can not only track the divers, but also send messages via the panel in the user interface.  Divers are able to respond from the diver module.

Untethered ROV Mode
FUSION can be acoustically commanded without use of a tether to go to markers, orbit markers, drop payload or execute missions (like AUV mode).

There are numerous possible applications for use of the TSNP for acoustic control, command, messaging and tracking.