Dear Bojan Andonovski

These articles might be useful, have a look:

1. https://tel.archives-ouvertes.fr/tel-02462079/file/main.pdf

2. https://mdpi-res.com/d_attachment/applsci/applsci-10-01256/article_deploy/applsci-10-01256.pdf

Kind Regards

Qamar Ul Islam

I would recommend Inertial-SONAR combination for underwater localization if possible in your setup. You can use visual sensor as secondary aiding.

Regards,

Good luck

Dear Bojan, your question has for answer "it depends..."

As any mobile, the UUV operates in its own relative referential that has to be reintegrated into absolute 3D geo-coordinates; the challenge is the poor propagation of electromagnetic waves underwater, leaving a key role to acoustics.

- HF Sonar imaging of the seabed allows localizing the UUV from a known rock or artefact with an accuracy of few centimetres, however you need to have a high accuracy local map of the seabed to relocate your UUV from sonar detection of such geo-localized natural or artificial markers; on-board processing is almost unachievable, you know your accurate position only when post-processing the sonar data;

- Sonar is distinct from acoustic telemetry: acoustic telemetry uses active pingers accurately located by GPS when deployed in the area of planned UUV operations and provide also a decimetric localization even in turbid waters but in the limited area insonified by the pingers deployed to ensure a proper triangulation; if your UUV is navigating in a precise area of few km2, it is by far the best solution as providing real time positioning; commercially these systems are also known as "underwater GPS"; this imposes anyway to add the receiver and processor in the UUV payload;

- Doppler loch is a navigation sonar contributing to navigation accuracy - specially to detect and compensate the drift due to marine currents; however it is probably difficult to add it to your UUV sensor package;

- IMU devices provide a localization capability with an accuracy decreasing with time from launch and currents: localization errors of more than 10m are common after a couple of hours of complex navigation in a coastal area! It can be corrected if you relocate periodically the UUV thanks to absolute re-localizations from the sonar detection of geo-localized markers on the seabed (point1 above); or alternatively re-sinchronize with GPS by surfacing regularly;

- Your video camera will not help in turbid waters but can help to confirm passing specific waypoints such as the markers identified by sonar: the detection range is anyway very limited compared to sonar! And (to the contrary of sonar) a camera is not providing the precise distance of the detected marker, I would not count much on it...

As an affordable and accurate solution I would recommend the ”Underwater GPS“, that we are using with a BlueRov2: https://shorturl.at/floIJ