Hereflow questions


I am using a Hereflow optical sensor and is currently trying to tune the FLOW_FXSCALAR and FLOW_FYSCALAR values accordingly.

Do these values affect the OF.flowX/OF.flowY or OF.bodyX/OF.bodyY?

Also, how can set my EKF Origin if i do not know my current location? (no gps)

First update to at least ArduCopter 4.1.5.

On mission Planner right click on the desired position on the map and click “set home here”

You clearly have not read the documentation, please do.


I have already updated to arducopter 4.1.5

I also do know that i can set the ekf origin by right clicking on the map on mission planner, but what i meant to ask was in the event where i do not have gps, such as indoors, is the exact location of where my drone is important?

No, it is not important, but it must be close to the real location. Have you disabled EKF2?
Are you using EKF3?


Ok thanks for the clarification

my AHRS_EKF_TYPE is currently 3, but my EK2_ENABLE is 1, do i need to disable EKF2?

Please disable EKF2 completely. And make sure EKF3 is enabled and used.


Ok will do that and try again.

Is it wise to adjust the EK3_FLOW_I_GATE and EK3_FLOW_M_NSE values too?


Does anyone know how FLOW_FXSCALAR/FLOWFYSCALAR will affect the flight behaviour of the aircraft? For example, will it try to hold position more aggresively?

Also, has anyone tried making use of EK3_FLOW_I_GATE and EK3_FLOW_M_NSE? And if so, is it possible to improve the behaviour of the aircraft? (less drifting)

Hi @limzw,

In general you shouldn’t need to adjust the GATE and NSE values.

The scalar values will affect how well the vehicle flies because it affects how well the EKF can estimate its position.

There are really two large components to any drone system, the EKF which is responsible for the estimation of the position, speed, angle, etc. Then there’s the control component which is responsible for controlling the vehicle’s position, speed, angle, etc. These scalars, gate and noise all just affect the estimation portion. They don’t affect how aggressively the vehicle will try to hold position.

Hi @rmackay9 ,

Thanks for the clarification!

How can i help to further reduce drifting when making use of the Hereflow? I’ve seen on other posts that adjusting the FLOW_POS_X/Y/Z accordingly will help also, but I’ve done that and it doesn’t seem to help very much.

P.s. the flights i’ve done are indoors, so i suppose the lighting may not be that great for the Hereflow to function accurately also


Yes, setting FLOW_POS_X/Y/Z values is important. 4.2.0 (now in beta testing) also includes an inflight flow calibration procedure so that may help to get good scaling.

Does anyone know which diagram is correct for the FLOW_ORIENT_YAW = 0?
diagram A or
diagram B

Isn’t it X is forward?

Hi @limzw

Do you manage to reduce the drift? if yes, are you able to share how you did it?
I am trying to do it too.

Hi @Jai.GAY,

Unfortunately i did not manage to reduce the drift, i have also not continued testing since then.

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I see no mention in this discussion of setting a EK3_SRCx_VELXY parameter to use flow. As a brand new optical flow user, maybe my fresh set of eyes caught the problem?

@Yuri_Rage, I think rmackay9 indirectly mentioned it in his link.