SVO+ethz_msf absolute scale (height) setup

[XinkeAE]

Hi,

Thanks for sharing your work!

I have a question about setting up the absolute scale in the ethz_msf while the visual measurement is provided using SVO. While using PTAM, the reference coordinate (0,0,0) is located on the ground plane and we can use the "core_set_height" and an external reference measurement to initialize the absolute scale.

We've performed a few preliminary tests using the SVO package and have noticed that the SVO determines the reference coordinate frame a little differently than PTAM. When initializing SVO, the origin is set at the position of the camera rather than on the ground plane (like PTAM).

I was wondering if SVO can be set up such that the reference coordinate frame is generated on the ground plane as well. If not, how is the scale parameter set-up in ethz_msf?

Thanks!
Xinke

[cfo]

I was wondering if SVO can be set up such that the reference coordinate frame is generated on the ground plane as well. If not, how is the scale parameter set-up in ethz_msf?

With the current configuration parameters such a setup is not possible. The origin will always coincide with the first camera frame. However, you can set the map_scale parameter which sets the distance of the camera to the ground-plane during initialization (in meters). More tips on how to setup SVO with MSF are given here: https://pixhawk.org/dev/ros/visual_estimation

For instance, you probably want to set the initial camera orientation to downward looking by setting the parameter init_rx =3.14 (rotate 180deg around x-axis). Furthermore, to work with MSF you need to set publish_world_in_cam_frame=False.