I’ve been working with the flowdeck v2 to try and figure out how to obtain the flow divergence in the vertical direction of the optical flow vectors that are sensed from the camera. The flow divergence is equal to vz/z, where vz is the vertical downward velocity and z is the height above the ground. In other words, I’m looking for an output from the flow sensor which correlates with vz/z.
Looking at the variable groups that can be logged from the flowdeck, I can see that there’s deltaX and deltaY in flow/fr that I can log. I can also see that there’s motion.Rawsum that gives me the raw sensor data from the flow deck.
Here’s what I have tried so far:
- I’ve tried taking the hypotenuse of the quantities deltaX and deltaY to see if it correlates with vz/z. I don’t think this is working.
- I’ve tried logging motion.Rawsum and seeing whether its derivative correlates with vz/z.
- What are the units of the number (unsigned int 8-bit) that’s being logged from motion.Rawsum? Is it number of pixels?
- Is there a way I can extract the value of flow divergence — vz/z — from the optical flow sensor alone? (I don’t want to use the TOF sensor or anything else.)