# 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 or pull from the tether.

Using the Tracker 650, we can lock into a nearby plane like a seabed and hold position while the operator is doing other tasks.

**Requirements in addition to the DVL**: 

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

If installed on an ROV Ethernet network that has mavlink2rest, the DVL can automatically connect to [mavlink2rest](https://github.com/patrickelectric/mavlink2rest), a component of [BlueOS](https://github.com/bluerobotics/BlueOS-docker). See [this page](/c/tracker-650/using-mavlink-and-blueos-for-position-hold-on-a-bluerov2.md) for details.

The DVL can also output $[DVPDL ](/c/tracker-650/communicating-with-the-tracker-650/outgoing-message-formats-tracker-650-to-host/usddvpdl-and-usddvpdx-dvl-position-and-angle-deltas-messages.md)(Position Delta) or $DVPDX (Extended Position Delta) messages which contain position delta and orientation data in ROV coordinates. This message can be used by a flight controller for position holding, and to use it, you the user will need to provide a software integration to connect the Tracker 650 messages to your flight controller.


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