Glossary of ROV terms


Hey folks, we’re putting together a glossary of terms for newcomers and super-users alike to reference with talking about underwater exploration with ROVs and some of the terms that OpenROV’ers use without thinking whether they are easy to understand.

This is going to be a crowd-sourced project over the next few months. Please take some time to critique and add to this list as I’m sure the jargon can become very troubling for some people, myself included. In the mean time, please hand me the thing that looks like a spring and goes in the bottom of the battery tube…you know the negative battery terminal.

BeagleBone Black. This is the latest single board Linux computer from BeagleBoard that is the platform on which the OpenROV cockpit software runs. You can find more here.

Electronic speed controller. This device converts control signals (such as PWM) into mechaincal movements in the motors. The OpenROV uses the Afro 12A ESC.

Controller Board
The controller board (sometimes “control board”) is the motherboard of the OpenROV electronics package. It contains a microcontroller similar to an Arduino Mega that handles all the low-level commands sent from the cockpit such as general purpose digital inputs and outputs, servo control, pwm channels for motors, and a myriad of other features. The controller board also handles voltage regulation, protection circuitry, and sensor integrations.

Pulse width modulation. This is the process that sends a signal based on a duty cycle. For example: 100% is a continuosly “on” or “off” signal whereas 50% is on/off switching on then off for the same period of time each. OpenROV uses this signal to control the power to the motors via the ESC.

Scaling Lasers
Lasers that are placed parallel and a known distance apart, usually in the line of sight of the camera. This allows for the measuring of size underwater by way of measuring the distance between the dots “painted” on the target.

In ROV operation, the search pattern most similar to the mowing the lawn where large areas are covered by many passes of the same vehicle. The vehicle travels in a straight line and when reaching the end of the search area makes a 180 degree turn and returns the direction opposite that it arrived but slightly to one side as to cover a new area on it’s return.

The type of connector that is on the end of an Ethernet or network cable. The OpenROV uses an RJ-45 jumper to connect the BeagleBone Black to the Homeplug Adapter.

Homeplug Adapter
This device is traditionally used to create an Ethernet connection along the electrical wires in a house or home office. The OpenROV uses this device to communicate quickly across cheap and lightweight two-wire tether.

The wires that go from the ROV to the topside electronics. Sometimes this can be called an “umbilical.” Traditional ROVs typically use fiber optic cable and can often have strengthening members made from Kevlar.

An image can refer to the software than runs on the BeagleBone Black.

Firmware is a set of instructions similar to software but intended to be largely unchanged over time. OpenROV utilizes firmware both on the controller board and on the ESCs.

The name of the user interface that OpenROV uses to interact with the ROV.

Inertial measurement unit. A collection of gyroscopes, magnetometers, and accelerometers that are used in concert to determine motion changes and orientation of an ROV.

In our guides, using a material that cures or hardens to create a barrier between an air space and water. Potting can be used to completely enclose or encapsulate an object or to create a pass-through for wires or other materials.

The type of connector used on the main wiring harness of the OpenROV. It has 25 pins and connects to the DB-25 receptacle on the controller board. Often times this is called the “wiring harness” or “DB-25 cable”

Left hand side on a boat when oriented in the direction of travel.

Right hand side on a boat when oriented in the direction of travel.

Speed Factor
The speed or thrust factor is the general level of power sent to the motors. This is configurable in cockpit.

Abbreviation for the electronics tube that is the acrylic tube that houses all the electronics of the OpenROV. This can sometimes be called the main tube.

The weight added to an ROV to make it neutrally buoyant or to sit level and not to one side or the other. Sometimes this foam or other flotation can be added to compensate for this in the other direction.

Topside Interface (Board)
This is the small electronics package that stays near the computer or latptop on the surface. It’s purpose is to connect the ROV and the computer via Ethernet.

A chemical or material that absorbs water-vapor or moisture. Often found in a cereal box and is inedible. Can be used to remove moisture from the main tube when used correctly.


Remotely Operated Vehicle. Typically a camera mounted in a waterproof enclosure with thrusters for maneuvering. Typically connected to the surface with a tether. Often times the mode of operation is known as tele-operation or tele-robotics, where a user is using video feedback, sometimes in tandem with sensor data, to control the ROV.

Autonomous Underwater Vehicle. It differs from the ROV in that a fully or semi-autonomous mode of operation is used. The vehicle uses on-board sensors to execute a pre-defined mission. These are typically used for continuous or long operations where data collection or discovery is important.

Working Class ROV
These ROVs are larger and more stable and feature the ability to manipulate their environment such as grippers and heavy tooling.

Observation Class ROV
Observation class ROVs are smaller and designed for positioning themselves in a meaningful place and relaying visual data back to the operator. Observation class ROVs can also include light payloads and sensor packages to aid in their mission.

Degrees of Freedom
The degrees of freedom refers to the different directions the ROV can maneuver. In ROV operation it can be rotational, such as pitch (tilt up and down), roll (lean left and right), or yaw (rotate left and right) or translational such as heave (move up and down), sway (slide to the left and right), and surge (move forward and backward).

Clump Weight
A weight attached midway along the tether designed to give the ROV more stable operation. The clump weight sits on the bottom and the tether between the weight and the surface has no effect on the vehicle and thus the tether drag between the ROV and the clump weight is smaller than it would be from the vehicle to the surface. This technique can be useful when trying to keep the ROV in a confined area of operation or mitigating the effect of strong currents.


The Inter-integrated Circuit (I2C) Protocol a communication protocol that allows multiple “slave” digital integrated circuits to communicate with one or more “master” chips. It is only intended for short distance communications within a single device. Currently the OpenROV IMU uses the I2C channel, but theoretically any I2C device can be connected in addition or in place of.


O-rings are used to keep water from getting into the battery tubes or the electronics tube. They are made from a pliable rubber material and are a ring with a circular cross section. O-rings do need to be replaced when they fail.