Question:

I would like to try apriltag with my raspi and raspi-camera. Here is the workflow.

1. Images would be taken from raspicam with 10Hz.
2. Use Image_proc package to rectify the images
3. Use Apriltag_ros to detect tags

The following link is the picture of my rqt_graph. https://drive.google.com/file/d/1XQoE...

After following the steps in the Appendix C in this post. I got the following error message and the [WARN] message continuous showing up. Also, there is no result from topic /tag_detections.

[ INFO] [1629181934.407924029]: Loaded tag config: 1, size: 0.075, frame_name: tag_1
[ INFO] [1629181934.408216996]: Loaded tag config: 2, size: 0.08, frame_name: tag_2
[INFO] [1629181934.408368766]: Loaded tag config: 3, size: 0.075, frame_name: tag_3
[INFO] [1629181934.408532411]: Loaded tag config: 4, size: 0.075, frame_name: tag_4
WARN] [1629181934.414992843]: remove_duplicates parameter not provided. Defaulting to true
[WARN][1629181944.645441278]: [image_transport] Topics '/raspicam_node/image_rect' and '/raspicam_node/camera_info' do not appear to be synchronized. In the last 10s:
Image messages received: 94
CameraInfo messages received: 99
Synchronized pairs: 1
[WARN] [1629181954.645304305]: [image_transport] Topics '/raspicam_node/image_rect' and '/raspicam_node/camera_info' do not appear to be synchronized. In the last 10s:
Image messages received: 100
CameraInfo messages received: 100
Synchronized pairs:
[WARN][1629181964.645229364]: [image_transport] Topics '/raspicam_node/image_rect' and '/raspicam_node/camera_info' do not appear to be synchronized. In the last 10s:
Image messages received: 100
CameraInfo messages received: 100
Synchronized pairs: 0
[WARN] [1629181974.645151610]: [image_transport] Topics '/raspicam_node/image_rect' and '/raspicam_node/camera_info' do not appear to be synchronized. In the last 10s:
Image messages received: 100
CameraInfo messages received: 100
Synchronized pairs: 0
[WARN] [1629181984.644698753]: [image_transport] Topics '/raspicam_node/image_rect' and '/raspicam_node/camera_info' do not appear to be synchronized. In the last 10s:
Image messages received: 100
CameraInfo messages received: 100
Synchronized pairs: 0

Is there any body could give me some hint how to fix it? Any advice would be very appreciated.

Appendix A. Environment:

• HW: raspi 3B, raspicam

• SW: raspi ubuntu 16.0, ROS kinetic

• Camera driver & camera calibration tool: raspicam node from https://github.com/UbiquityRobotics/r...

• image_proc package: http://wiki.ros.org/image_proc
• apriltag_ros package: https://github.com/AprilRobotics/apri...

Appendix B. Setup:

1. create launch file under /opt/ros/kinetic/share/raspicam_node/launch

<launch> <arg name="enable_raw" default="false"/> <arg name="enable_imv" default="false"/> <arg name="camera_id" default="0"/> <arg name="camera_frame_id" default="raspicam"/> <arg name="camera_name" default="camerav2_320x240"/>

<node type="raspicam_node" pkg="raspicam_node" name="raspicam_node" output="screen">

<param name="camera_frame_id" value="$(arg camera_frame_id)"/>
<param name="enable_raw" value="$(arg enable_raw)"/>
<param name="enable_imv" value="$(arg enable_imv)"/>
<param name="camera_id" value="$(arg camera_id)"/>

<param name="camera_info_url" value="package://raspicam_node/camera_info/camerav2_320x240.yaml"/>
<param name="camera_name" value="$(arg camera_name)"/>
<param name="width" value="320"/>
<param name="height" value="240"/>

<param name="framerate" value="10"/>
<param name="exposure_mode" value="antishake"/>
<param name="shutter_speed" value="0"/>   </node> </launch>

1. Revise image_proc to listen to /raspicam_node/image topic

Appendix C ...