LBL Sparse Array Acoustic System

Vue d'ensemble

Ramses is a flexible acoustic modem with self-contained computing, designed to perform full-LBL or sparse-LBL navigation capabilities to any type of underwater vehicle (ROVs, AUVs...).

Tightly coupled with an iXblue inertial navigation system (INS), Ramses delivers extreme precision and robustness in challenging acoustic operational environments, and thus even with a greatly reduced number of transponders compared to other LBL systems.

Using Ramses, both LBL and sparse-LBL features are natively offered to the operator depending on the number of available transponders:

  • With 1+ transponder, sparse-LBL position is obtained from the fusion of acoustic ranges with navigation equations from the INS
  • With 4+ transponders, embedded LBL algorithms provide high performing 100% acoustic navigation and efficient environmental QC

Related news


Main performances

or INS aided
< 0.10


< 0.01






  • Smooth integration on ROVs and AUVs
  • LBL navigation accuracy, with reduced arrays and  superior precision
  • Flexible array deployment thanks to SLAM
  • High-speed acoustic  communications



 Ramses embedded on Ifremer's AUV IdefX

Sparse-LBL: a cost efficient and flexible solution for enhanced subsea autonomy

Nowadays, various positioning techniques are available for companies and institutes that need valuable navigation information to operate undersea. And while LBL usually remains the preferred solution for the highly accurate positioning of ROVs and AUVs, this method remains costly as it requires the use of many transponders to produce a single position. Operators are thus now looking for new ways that are more efficient, flexible and less costly to conduct their operations.


Acoustic synthetic baseline positioning system


  • What is the recommended procedure for hydrophone and transducer maintenance?

    For preventive maintenance;

    • In order to limit growth on the hydrophones, iXblue recommends to use the following anti-fouling:
    • International: TRILUX 33
    • SigmanCoatings: blue Sigma-glide

    They should be cleaned with isopropylic alcohol (Steps mentioned below)

    • Light abrasions with 100/120 sand paper
    • Clean with isopropylic alcohol
    • Wet the surface with aliphatic hydrocarbon solvent
    • Wait for 2 minutes to dry
    • Apply anti fouling according to the manufacturers recommendations (a thin coating)
    • Wait for 24 hours

    For curative maintenance:

    • To clean the hydrophones; use synthetic soap and water
    • To remove growth, use 180 sandpaper and apply minimal pressure on the hydrophone
  • What is Ramses maximum range?

    The maximum range is dependent on the noise level, of beacon transmit level and of the frequency band used for acoutic signals. For a TL = 191 dB ref µPa:

    •  if noise level is 70 dB ref µPa: max range is 3600 m (example of quiet vessel)
    •  if noise level is 80 dB ref µPa: max range is 2300 m (example of a quiet ROV)
    •  if noise level is 90 dB ref µPa: max range is 1300 m (example of a noisy ROV)
  • Where is the reference point of Ramses ?

    The reference point of the Ramses is the center of its acoustic head. Refer to Ramses user manual for drawings.

  • Which Navigation Software are compatible with Ramses?

    Almost all navigation softwares have Gaps driver (QINSY, NAVIPAC, HYPACK, STARFIX, WINFROG, GECDIS). As Ramses outputs Gaps $PTSAG in Ramses standard and PTSAG protocols, it is naturally compatible with those softwares. When coupled with an INS, the system benefits from all INS protocols as the otimum position of the vehicle is delivered by the INS itself.

  • What is the position output of INS-Ramses system ?

    When Ramses is coupled to an iXblue INS:

    • transponder positions are delivered by Ramses (e.g. on PTSAG frames)
    •  vehicle position is provided by the INS, being smooth and robust thanks to inertial sensors
  • Do I need to measure the sound velocity profile?

    Sound velocity can be compensated in different manners in Ramses:

    •  connecting Ramses to SVS output stream, the measured SV is used for distance computation
    •  Ramses can use measured SV profile, measured and loaded by the survey team in Ramses.
    •  when a single SV value is entered in SV profile configuration, this value is used as an average SV for distance computation. When working in deep water oil & gas fields, the manual setting of an average SV facilitates SV QC and adjustement to the calibrated array.
  • What to do if positioning accuracy is not as good as expected?

    If positions are jumpy, this probably comes from a multipath (reflective surface which is to close to the Ramses or the beacon) and/or difficult conditions for acoustic propagation (shallow water or horizontal tracking). Increase Ramses depth or place the beacon transducer differently.

    If a bias is observed in the positioning:

    • check beacon turnaround time (in the beacon and in the product web MMI)
    • check that a correct sound velocity profile has been configured into the system
    •  check lever arms and potential mounting misalignments
  • What comes in a standard Ramses delivery?

    Ramses standard package comprises Ramses body and head, with associated cables to operate the system (remote transducer cable, pigtail and test spider). Additional items and cables can be order separately (e.g. Ramses-INS-ROV splice cable,...).

  • What operating system does Ramses support ?

    iXblue systems are operated through an Internet browser (Firefox, Chrome, Internet Explorer, Safari…) and operated from any device that runs an Internet browser (laptop, workstation, computer, mobile, tablet...). This means that there are no restrictions regarding the Operating System. iXblue recommends the use of Firefox because this is our qualification environment.

  • What is the best location to mount Ramses transducer on ROV?

    As far as possible from any source of noise (thrusters, propellers, engines...) and on top of the ROV in order to get direct acoustic line of sight.