# Here Flow low light

**URL:** <https://discuss.cubepilot.org/t/here-flow-low-light/5214>\
**Category:** HereFlow\
**Created:** [27 November 2020 08:18 UTC](https://discuss.cubepilot.org/t/here-flow-low-light/5214 "2020-11-27T08:18:49Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![GREGORIS\_DEMETRIADES](https://discuss.cubepilot.org/user_avatar/discuss.cubepilot.org/gregoris_demetriades/32/1048_2.png) [@GREGORIS\_DEMETRIADES](https://discuss.cubepilot.org/u/GREGORIS_DEMETRIADES)\
**Post date:** [27 November 2020 08:18 UTC](https://discuss.cubepilot.org/t/here-flow-low-light/5214/1 "2020-11-27T08:18:50Z")

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So to fully understand. Here Flow doesn’t work at no light conditions (at night). It seems that in auto modes like Land or RTL although i have an SF11C lidar when the quad lands it bounces back and forth. It happened 2 times that i tried it.

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**Author:** ![Alvin](https://discuss.cubepilot.org/user_avatar/discuss.cubepilot.org/alvin/32/1000_2.png) [@Alvin](https://discuss.cubepilot.org/u/Alvin)\
**Post date:** [1 December 2020 05:39 UTC](https://discuss.cubepilot.org/t/here-flow-low-light/5214/2 "2020-12-01T05:39:43Z")

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Do you have video and log?  
Could it be ground effect regaining altitude for your copter?

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**Author:** ![snakeeater](https://discuss.cubepilot.org/letter_avatar_proxy/v4/letter/s/898d66/32.png) [@snakeeater](https://discuss.cubepilot.org/u/snakeeater)\
**Post date:** [5 December 2020 03:09 UTC](https://discuss.cubepilot.org/t/here-flow-low-light/5214/3 "2020-12-05T03:09:44Z")

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I noticed if you have any lights on the copter they will be reflected from the ground at low altitude, but because those reflections move with the copter this occasionally completely messes up position estimates. Same could apply if the flow sensor locks on the copters shadow. Also above water when there are waves this can completely mess up the position.

I am already thinking if the slight position imrovement in ideal conditions is worth the risk of the copter going rouge in not so ideal conditions.

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**Author:** ![Loris\_Demetriades](https://discuss.cubepilot.org/user_avatar/discuss.cubepilot.org/loris_demetriades/32/1193_2.png) [@Loris\_Demetriades](https://discuss.cubepilot.org/u/Loris_Demetriades)\
**Post date:** [6 December 2020 08:54 UTC](https://discuss.cubepilot.org/t/here-flow-low-light/5214/4 "2020-12-06T08:54:39Z")

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@Alvin @snakeeater The problem should be the lights facing downwards, (two green and two red), that @snakeeater is right, they create various circle patterns as the copter is very close to land and flow sensor gets confused.

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**Author:** ![snakeeater](https://discuss.cubepilot.org/letter_avatar_proxy/v4/letter/s/898d66/32.png) [@snakeeater](https://discuss.cubepilot.org/u/snakeeater)\
**Post date:** [6 December 2020 10:18 UTC](https://discuss.cubepilot.org/t/here-flow-low-light/5214/5 "2020-12-06T10:18:08Z")

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I already masked all lights in the downward direction, but in complete darkness even minimal light scattering can cause trouble if you are over flat floor, like tiles. Ill try doubeling the FLOW\_NSE parameter to weight flow readings less and hopefully get a bit better resiliance.