[Remotely operated underwater vehicles used in water rescue].

Background: The search for and rescue of missing persons is always coupled with a high demand on human resources. In cases of suspected drowning it is often necessary to search huge expanses of water. For depths of more than 3-5 m the search and rescue procedure needs to be performed by specialist rescue divers. Due to saturation with nitrogen caused by the higher ambient pressure during the dive, the operating time for each rescue diver is limited. In addition, each dive is linked with an increased risk.

Objective: Miniaturization of sensors, higher performance of embedded systems and high energy density of modern accumulators offer the chance to operate with unmanned flying and diving vehicles for search and rescue even with moderate financial investment.

Material and methods: Based on funding by the Federation of the German Live Saving Association (DLRG) the DLRG national association of Bavaria procured three different models of remotely operated underwater vehicles (ROUV) and two different systems for underwater positioning. These systems will be offered to local associations of the DLRG in Bavaria for intense testing in their waters based on a common implementation strategy to ensure comparability and reproducibility.

Results: Initial tests with different types of ROUV and underwater positioning have been performed in preparation of the survey. As a result, mini-ROUVs found in the lower consumer segment have been identified as insufficient as they are not able to carry the additional payload of the underwater positioning systems whilst maintaining controllability. In contrast, more complex drones are difficult to handle and require longer preparation times before they are ready for use. The ROUVs in the median range, preferably with a streamlined structure, have so far been found to be optimal; however, operating the vehicle without a positioning system is not recommended.

Conclusion: In combination with an underwater positioning system, remotely operated underwater vehicles are identified as a reasonable supplement for rescue divers. Fast time to operation enables a preview of the operating area before starting the rescue operation and can therefore support the rescue diver team.