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?

[Judoor 0]

@Alex-Kushleyev Is there some news about this issue ?

[tomverstappen]

Is there already a solution for the problem from Kessie?

Is there anyone that has a working setup for AprilTag relocalization on the tracking_down camera?

[Zachary Lowell 0]

Hello All - I will be trying to recraete this issue in the coming days - will keep you all posted.

[Zachary Lowell 0]

@tomverstappen I am unable to recreate the issue with a starling running 1.5.0 - the output from voxl-vision-hub shows the relative coordinate frame from the tag relative to the camera and was able to get the drone to offset correctly.

Are there any logs you can paste in here or video?