# PX4 Vision optical flow not working

**URL:** <https://discuss.px4.io/t/px4-vision-optical-flow-not-working/32270>\
**Category:** PX4 Autopilot\
**Created:** [May 18, 2023, 9:30am UTC](https://discuss.px4.io/t/px4-vision-optical-flow-not-working/32270 "2023-05-18T09:30:11Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![stefano\_roccella](https://discuss.px4.io/user_avatar/discuss.px4.io/stefano_roccella/32/12922_2.png) [@stefano\_roccella](https://discuss.px4.io/u/stefano_roccella)\
**Post date:** [May 18, 2023, 9:30am UTC](https://discuss.px4.io/t/px4-vision-optical-flow-not-working/32270/1 "2023-05-18T09:30:11Z")

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Dear all,  
I am trying to use PX4Vision indoor without GPS. I changed EKF2\_AID\_MASK to optical flow only. PX4Vision uses PMW3901 and SF20/C Lightware Lidar on I2C. In mavlink inspector I can see DISTANCE\_SENSOR and LOCAL\_POSITION\_NED topics working. I take off in Position Mode but drone drifts on the right with high velocity so I have to switch back in altitude in order to take control. In other words it is not able to keep hovering. Room is illuminated and the floor has texture.

Can you help me in solving the issue?  
Thanks a lot and regards  
Stefano

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<div class="post-metadata">

**Author:** ![stefano\_roccella](https://discuss.px4.io/user_avatar/discuss.px4.io/stefano_roccella/32/12922_2.png) [@stefano\_roccella](https://discuss.px4.io/u/stefano_roccella)\
**Post date:** [May 22, 2023, 3:58pm UTC](https://discuss.px4.io/t/px4-vision-optical-flow-not-working/32270/2 "2023-05-22T15:58:21Z")

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Have you any suggestions to help me? It is an important project and I need to fly indoor.

Thanks a lot,  
Regards  
Stefano