Offboard mode with optical flow

PX4 Autopilot Flight Controllers 💻
1

Hi, I am planning to do indoor 3D path planning project with pixhawk with jetson kit and optical flow for position control. My optical flow is [MicoAir] MTF-01.

My question is how optical flow and pixhawk calculate altitude. As far as I know, tof sensor calculates distance between underneath object and drone. So, I think drone goes up when the drone fly over object. For example, if I command pose.pose.position.z = 1, the drone can’t maintain 1m above ground if there is any object under the drone while flying.

Am I right? or does pixhawk can calculate absolute distance from the initial point?
I am considering using VIO instead of optical flow.

Thanks!

2

Flow is just velocity (delta position estimates) of the sensor. You need something to get it to scale, so some sort of distance measurement. Usually, that’s a laser range finder, sometimes sonar depending on the surfaces you fly on.

3

Thank you @JulianOes !
I also use down facing lidar as a range finder.
What happens if the drone fly above a hill? Does the drone go up because the slope reduces the distance between the drone and the hill?

4

Have a read through this: Terrain Following/Holding | PX4 User Guide (v1.14)

5

Thank you for the response! I will check the post:)