Fiber-optic spools to help search for missing persons

Each year, many disparearances are related to risky activities or natural phenomena such as drowning, caving accidents, incidents at sea or landslides.

In France there are:

• Landslides/land movements/floods: these events are rarer but can be dramatic, with dozens or hundreds of potential victims in case of disaster (e.g. Martinique or Mayotte).
• Caving: there are around 20 to 30 rescue operations and around 15 self-rescues per year, with 1 to 2 deaths recorded annually.
• Drownings: between 900 and 1,000 drownings each summer in France, causing around 250 to 270 deaths.
• Accidents at sea (professionals and recreational boaters): around 10 deaths or missing persons per year among professional sailors, with several thousand rescue operations for recreational boating activities.The safety and rescue measures in place to find missing persons are not always the most appropriate for complex access situations.

Conventional methods used to locate missing persons include:

• Helicopter searches to scan a large search area, then gradually narrow down the search radius;
• Drone searches, which allow access to areas that helicopters cannot reach;
• Submarine searches for people missing at sea (drowning, etc.)
• Searches by patrol, requiring the mobilisation of human resources and dog teams (sniffer dogs).

The implementation of these methods depends on the search area and environmental constraints.

However, these material and human resources are limited. Indeed:

• Helicopters cannot operate anywhere and cannot examine an area very precisely given the safety distance that must be maintained in order to avoid endangering teams and, above all, to avoid a crash. In addition, helicopter time is prohibitively expensive.
• Drones are not reliable enough in terms of continuous signal and information transmission between the control station and the drone (confined areas, interference, loss of network, power cable stuck preventing the mission from continuing and the device from being recovered, etc.).
• Marine drones only operate in marine environments and can encounter the same problems as aerial drones (confined areas, wrecks, sea caves).
• Patrols require the deployment of personnel on the ground, which means putting them in danger in certain situations (landslides, earthquakes, etc.). This option is also a race against time.

Search and rescue operations at sea are highly challenging because many factors must be taken into account in order to rescue a person without putting them in further danger.

Changing and extreme weather conditions are very important because they can either help or hinder the search for missing persons at sea and limit the resources available. The vast expanse of the sea and the uncertainty of location, sea currents and the rapid drift of objects or people, the critical time for the survival of people at sea, often reduced visibility (night, fog, swell) and limited access to certain areas are also constraints that complicate searches and mean that the conventional means available are not the most suitable.

Indeed, reconnaissance by helicopter or drone does not allow access to hard-to-reach areas or deep visibility due to very limited visibility and the risk of radio signal loss between the control station and the drone (dead zones). These challenging locations sometimes require the use of multiple devices depending on the conditions encountered (e.g. a drone for the air, then a marine vehicle to go into the water).

Currently, these drones and underwater vehicles are powered electronically. However, these devices are forced to follow the same route there and back, as the power and data transmission cable acts as a leash, which can become stuck or blocked and prevent the device from returning to its base.

Most existing drones and remote-controlled vehicles cannot access this type of winding and steep terrain, or can only do so with great difficulty, because the data transmission or power cable is too rigid and acts like a leash. In fact, the vehicle is forced to retrace its steps to return to its base, which adds a significant constraint.

Installing this type of equipment is also very restrictive and can hinder the smooth running of the mission:

• the power and data transmission cable is wound onto a winch. If there is a knot or if the cable has been rewound incorrectly, the operation is compromised because the drone or vehicle is blocked and cannot move forward. It must be returned to base.
• this solution is extremely heavy and cumbersome and must be securely anchored to the ground for the operation to run smoothly.
• as the fibre unwinds from the ground, it acts as a leash for the drone, which must also retrace its exact path in order to be recovered.
• at the end of the operation, the fibre and cable must be immediately ‘rewound’ onto the winch before releasing it from the ground.

As access to caves, caverns, wrecks, etc. is restricted, there is little chance of obtaining key, usable information without risking jamming the device and having to retrieve it, putting human lives at risk in the process.

As with sea searches, reconnaissance by helicopter or drone does not allow access to difficult-to-reach or very steep areas such as caves or underground cavities. Accessing these challenging and steep areas requires the use of several devices, but also sometimes human intervention, putting people at great risk.

Searching for missing persons in forests, with caves and underground cavities that could serve as shelters for the missing, is very complex and time-consuming. However, it is a race against time because without water or food, it is impossible to survive for very long. This is especially true if the person being searched for is injured and in urgent need of medical attention. This is why it is essential for rescuers to recognise, locate and identify danger zones and assess the specific resources to be deployed. For this purpose, a tethered drone is ideal.

As floods are the cause of many accidents, a hybrid drone is required.

Where there is a loss of radio signal between the radio-controlled drone and the control station when flying over uneven terrain (mountainous, steep, hilly, etc.), fibre optics is a secure and reliable solution, as it does not require radio waves to operate and continues to transmit data to the control station in real time, without interruption, even in areas with no signal coverage.

Fibre optics offer a unique solution for real-time surveillance, as they can transmit ultra-high-resolution images and videos to ground operators without compression or loss of quality, unlike radio or cellular network transmissions, which are often limited in bandwidth.

Fibre optics can be installed on any vehicle or drone, whether land-based (UGV), marine (UUV) or aerial (UAV). All these vehicles can be equipped with fibre optics for remote control.