Meaning of 'Local Position X' (and 'Local Position Y) in the Flight Log

#1

So I am really unsure about the plots labelled as the ‘Local Position X’ and ‘Local Position Y’ which are visible in the flight logs. Are they the graphs of the coordinates of X and Y from the data of IMU, or from the data of the external sensors (SLAM/Visual odometry), or of the data from the computation of both, IMU and external sensors?

Flight Controller: Pixhawk 2.4.8
External X-Y directional sensor: Intel Realsense d415 Depth Camera
On-board computer: Intel NUC

Thank you in advance!

#2

pretty sure Local Position is referenced to where/when the EKF initialized. The EKF uses a fusion of many sensors. I’m not sure if Local Position updates/changes based on certain events. I bet someone with more knowledge could provide a more detailed response to your question.

#3

Thank you for your response! Much appreciated!
What does initialisation of EKF mean in this context? Does it happen when the Pixhawk boot up? And is this the EKF’s data what we see in the logs as Local Position?

Thank you in advance!
-J

#4

The EKF2 uses the IMU, GPS, as well as external vision estimates such as provided by PX4Flow and calculates an attitude and position estimate from it. When the EKF2 gets position information e.g. from a GPS it starts estimating the local position estimate. The origin of this “local position” is set where the EKF initializes. (This is not the “home” position which is reset on arming.)

For your case, I don’t think that the Realsense Depth information is incorporated into the local position estimate.

#5

Hey @JulianOes,

We are sending the SLAM data (using the realsense depth camera) to the /mavros/vision_pose/pose. So, this data should be used during the local position calculation, right?

#6

In that case that’s possible and I was probably wrong.