ROVs vs AUVs

Remotely operated vehicles

An ROV is linked to the surface by a tether that carries power, data or both, so a pilot sees live video and steers in real time. That makes ROVs well suited to close visual work: inspecting a hull, checking a net pen, looking inside a tank or recovering a small object. The tether is also the main limit. It sets the working range, adds drag in current and must be managed around structures. Compact observation-class ROVs can often be deployed by one or two people from a quay or small boat.

Autonomous underwater vehicles

An AUV carries its own batteries and navigates without a pilot, following a programmed route and recording data as it goes. With no tether, AUVs can cover long survey lines, map the seabed or sample the water column over wide areas. The trade-off is that you usually see the results only after recovery, and communication is limited, since radio and GPS signals do not reach far below the surface. Navigation typically relies on inertial sensors, acoustic positioning and sensors that track the seabed.

Choosing between them

Start with the question you need answered. If you need to look closely at something specific and decide what to do next, a piloted ROV usually fits. If you need consistent data across a large area, an AUV is often the better tool. Then check depth rating, thrust against the currents you expect, camera and lighting quality, payload options such as grippers or sonar, and how the vehicle is launched and recovered. Some newer vehicles blur the line, offering autonomous functions on a tethered platform.

Sources and further reading

• What is an ROV? — NOAA Ocean Exploration.
  Short explainer on remotely operated vehicles: uncrewed, tethered, joystick-piloted and fitted with cameras.
• What is an AUV? — NOAA Ocean Exploration.
  Short explainer on untethered vehicles that store their data onboard and work without a pilot.
• IMCA R 004: The safe and efficient operation of remotely operated vehicles (Rev. 6) — International Marine Contractors Association (IMCA).
  Industry guidance on ROV classes, tools, crew roles and safe working practice for offshore operations.

Common questions

Is an underwater drone the same as an ROV?

Usually, yes. "Underwater drone" is the everyday name for a compact ROV: a tethered, camera-equipped vehicle steered from the surface with a controller or tablet.

Why can't underwater robots use GPS?

GPS signals do not travel far through water. Underwater vehicles rely on inertial sensors, acoustic positioning and seabed-referenced sensors instead, sometimes surfacing to take a fix.