# Scenario: Holding Position

When flying aerial drones, it is typical to be able to release the controls and have the drone hold its position. For ROVs, since we normally don’t have an external position reference equivalent to the drone’s GPS, when we release the controls, the ROV often drifts due to currents and pull from the tether.

Using the DVL, we can lock into a position and hold it while the operator is doing other tasks.

**Requirements in addition to the DVL**: 

* Flight Controller with Position Hold capability
* Flight Controller which can interpret the [VISION\_POSITION\_DELTA](https://mavlink.io/en/messages/ardupilotmega.html#VISION_POSITION_DELTA) MAVLink Message. 

The DVL will automatically connect to [mavlink2rest](https://github.com/patrickelectric/mavlink2rest), a component of [BlueOS](https://github.com/bluerobotics/BlueOS-docker). See [this page](/c/dvl-75/using-mavlink-and-blueos-for-position-hold-on-a-bluerov2.md) for details.

The DVL can output a $[DVPDL ](/c/dvl-75/communicating-with-the-dvl/outgoing-message-formats-dvl-to-host/usddvpdl-dvl-position-and-angle-deltas-message.md)(Position Delta) message which contains position and orientation data in ROV coordinates. This message can be used by a flight controller for position holding. 


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