# Is an Optical Flow Worth Fitting?

Hi,

I am scratch building my first autonomous hexacopter using APM 2.5. I understand the principles of the optical sensor but cannot find much information online regarding its performance when used with APM:Copter 3.1 and the 2.x hardware.

My flying will be outdoors in daytime. I would like to know if the position holding performance gains make it a worthwhile sensor to fit?

My current view is that the lack of info / videos suggest not - am I correct in this assumption?

Zeke.

Hi Zeke,

Unfortunately PX4Flow is not currently supported by APM:Plane, APM:Copter, and APM:Rover firmware.

The PX4 team has information of how to use the sensor with PX4FMU and Pixhawk (no APM support) and the PX4 firmware:
pixhawk.org/modules/px4flow

I think, he was talking about the old optical flow sensor, not the PX4FLOW.

Sent from my Ainol Novo 7 Fire using Tapatalk

Oh sorry, this is the information we have in the wiki:
copter.ardupilot.com/wiki/optical-flow-sensor/

That Wiki link has gone dead, is there a wiki currently for APM optical flow?

Joel Silverman

@silvermanphoto,
If you are going to DIY you need to be a little more aggressive when searching for information and not give up so easily: http://copter.ardupilot.com/wiki/common-optional-hardware/common-optical-flow-sensors-landingpage/
Regards,
TCIII GM

TCIII,
can you confirm what last 3.2.1 APM version cover optical flow sensor? Ma be you know any custom version wit OF_loater covering shared for all??

The Optical Flow block estimates the direction and speed of object motion from one image to another or from one video frame to another using either the Horn-Schunck or the Lucas-Kanade method.
To compute the optical flow between two images, you must solve the following optical flow constraint equation:

I
x
u+I
y
v+I
t
=0
.

I
x
, I
y
, and I
t
are the spatiotemporal image brightness derivatives.
u is the horizontal optical flow.
v is the vertical optical flow.