# Motion Capture (MoCap)

Motion Capture (MoCap) is a [computer vision](https://en.wikipedia.org/wiki/Computer_vision) technique for estimating the 3D *pose* (position and orientation) of a vehicle using a positioning mechanism that is *external* to the vehicle. It is commonly used to navigate a vehicle in situations where GPS is absent (e.g. indoors), and provides position relative to a *local* coordinate system.

*MoCap* systems most commonly detect motion using infrared cameras, but other types of cameras, Lidar, or Ultra Wideband (UWB) may also be used.

:::note *MoCap* is conceptually similar to [Visual Inertial Odometry (VIO)](/px4-user-guide/drone_parts/companion_computer/computer_vision/visual_inertial_odometry.md). The main difference is that in VIO the vision system runs on the vehicle, and additionally makes use of the vehicle IMU to provide velocity information. :::

## MoCap Resources

For information about MoCap see:

* [Using Vision or Motion Capture Systems for Position Estimation](/px4-user-guide/robotics/ros/ros1/external_position_estimation.md).
* [Flying with Motion Capture (VICON, Optitrack)](/px4-user-guide/development/advanced/computer_vision/motion-capture.md).
* [EKF > External Vision System](/px4-user-guide/advanced_config/tuning_the_ecl_ekf.md#external-vision-system)


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