Apriltag relocalization not relocalizing?

[Kessie]

Hi,
We have enabled en_tag_fixed_frame in voxl-vision-hub to use apriltag detection as a way to relocalize indoor.
Am i correct to assume that the following is a tag located on the ground at point 0,0,0?
"T_tag_wrt_fixed": [0, 0, 0],
"R_tag_to_fixed": [[0, -1, 0], [1, 0, 0], [0, 0, 1]]

What would be the rotation matrix for a tag located forward against the wall?
What's the best way to test that the relocalisation actually happens?

---

system-image: 1.7.10-M0054-14.1a-perf
kernel: #1 SMP PREEMPT Fri Sep 27 21:59:02 UTC 2024 4.19.125

hw platform: M0054
mach.var: 1.0.1

voxl-suite: 1.3.5

[James Strawson]

yes, that's the correct rotation matrix for a tag on the ground.

For a tag on the wall with a center 1m off the ground you can use:
"T_tag_wrt_fixed": [0, 0, -1],
"R_tag_to_fixed": [[0, 0, 1], [1, 0, 0], [0, 1, 0]]

The second video of this docs page walks you through the voxl-vision-hub command line args to help you debug relocalization.

[Kessie]

@James-Strawson Hi, we are testing this and are keep getting roll/pitch out of bounds while the tag is laying flat on the floor.

[Kessie]

@James-Strawson we are still trying to understand this behaviour.
After several tests, we noticed that with the default SDK 1.4.1 on Starling 2 Max with C29 camera config :

• If holding an apriltag in front of the front-tracking camera ([[0, 0, 1], [1, 0, 0], [0, 1, 0]]), we need to turn it counterclockwise 90 degrees to not have the "out of bounds" error
• If holding an apriltag at the bottom camera ([[0, -1, 0], [1, 0, 0], [0, 0, 1]]), we are unable to remote the error

We have found this as well : https://forum.modalai.com/topic/2653/stereo-tag-detection-warning-apriltag-roll-pitch-out-of-bounds?_=1741697621820
However, this code also keeps giving strange out of bounds errors.
Is it possible to show a working tag_locations.conf for both a tag on the ground and a tag against the wall?
We are not really experienced in the transforms needed and it seems like a problem with that

[Kessie]

@James-Strawson @Eric-Katzfey,
Can you show a working example on a dual camera config, please?
Both flat on the ground as against a wall.
This would help us a lot!

Thanks in advance,
Maarten

[Kessie]

We have managed to solve the transformations and now get the correct tag detection.
But even with fixed_frame_filter_len set to 1, QVIO and OpenVins are used and we see no relocalisation happening.

Does someone have a working example which we can look at, please?