`apriltag_tracking` package doesn't work

[wangzizhe]

Hi,

I struggled a lot, but the apriltag_tracking package never worked... (I want to enable my TurtleBot3 to track apriltags)

I think it is mainly because of the transform from the following lines of apriltag_tracking.py:

if self.get_clock().now() - self.start_time > Duration(seconds=DELAY):
   to_frame_rel = 'camera'
   from_frame_rel = 'tag36h11_0'
   try:
       tf2_msg = self.tf_buffer.lookup_transform(to_frame_rel, from_frame_rel, rclpy.time.Time())
   except TransformException as e:
       # self.get_logger().info(f'Could not transform {to_frame_rel} to {from_frame_rel}: {e}')
       print('No AprilTag marker found, looking for one...')
       return

The value of the static transform between base_link and camera I already set them to the right values.

Node(
	package='tf2_ros',
	executable='static_transform_publisher',
	name='base_link_to_camera_tf',
	# https://navigation.ros.org/setup_guides/transformation/setup_transforms.html
	# http://wiki.ros.org/tf#static_transform_publisher
	# Static TF Publisher (relationship between base link and camera doesn't change in time)
	# static_transform_publisher x y z yaw pitch roll frame_id child_frame_id
	# Publish a static coordinate transform to tf2 using an x/y/z offset in meters and yaw/pitch/roll in radians. 
	# (yaw is rotation about Z, pitch is rotation about Y, and roll is rotation about X). 
	arguments = ['0.073', '-0.011', '0.084',
				'0.000', '0.000', '0.000',
				'base_link', 'camera']

However, i keep getting errors. I'm pretty sure the apriltag_ros detects the right AprilTag:

Also if I run ros2 topic echo /detections I get the values constantly updating. So I'm sure AprilTag could be detected.

header:
  stamp:
    sec: 1705330141
    nanosec: 981887783
  frame_id: camera
detections:
- family: tag36h11
  id: 4
  hamming: 0
  goodness: 0.0
  decision_margin: 184.5729522705078
  centre:
    x: 855.1402853430145
    y: 603.4324452437951
  corners:
  - x: 755.0858764648438
    y: 706.0559692382812
  - x: 955.772216796875
    y: 703.2138061523438
  - x: 954.2670288085938
    y: 501.7604064941407
  - x: 753.432373046875
    y: 502.58419799804676
  homography:
  - 104.6427878042058
  - 1.071645325037038
  - 855.1402853430145
  - 2.0928464181488255
  - 101.42798848337623
  - 603.4324452437951
  - 0.004987543463421618
  - 0.000330147913311962
  - 1.0
---

I'm getting the same error message for a long time as the transformation never works rightly...

I'm very helpless now, tried every solutions which I can imagine and which I could find in the internet. But it never worked...

Do you have any ideas? Or you faced somehow similar issue during your development?
Much appreciated!