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Apriltag topics do not return any information but execute without errors or warnings

asked 2018-01-13 15:20:09 -0600

dpoiesz gravatar image

I can launch the apriltag_detector node without errors or warnings but the topics do not return any information. The command 'rostopics list' will show all the correct topics but they do not return any info. After the command 'rostopics echo /tag_detections_pose' nothing happens, the terminal just reacts as it does when it is processing something ad infinitum. If I use web_video_server I can view /image_raw but if I select /tag_detections_image the browser will also continual load but never show anything. The camera was calibrated. I would appreciate any advice in correcting this problem, thank you.

System info:

ROS Kinetic, Ubuntu Mate 16.04 LTS, Raspberry Pi 3, Raspberry Pi camera

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answered 2018-01-14 04:53:29 -0600

For some reason the apriltag_detector node is simply not detecting any tags, this is exactly the behaviour you would expect in this case. Here are a few things to check:

Is the correct camera image topic being published alongside the camera images? Are the camera topics correctly mapped to the topic names the detector node expects? Are the camera images well exposed, not noisy and reasonably in focus? Have the size and type of fiducial markers been setup for the detector node?

Also if you could add one of the camera images and info messages to your question then we could confirm that side of things is okay.

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I'll start looking into those questions, I am still a novice and it may take me a bit to figure out how. What has me most confused is the apriltags detector did work before calibrating the camera but he positions were all zeroes.

dpoiesz gravatar image dpoiesz  ( 2018-01-14 13:16:01 -0600 )edit

I must have altered something by mistake when I was having problems calibrating the camera because I started getting errors when launching the apriltags detector. I deleted the catkin_ws and started over, and started fresh on a different SD card and am getting these new results on both.

dpoiesz gravatar image dpoiesz  ( 2018-01-14 13:19:58 -0600 )edit

Before the /tag_detections_image would display the video even if there was no tag to detect now it doesn't even load.

dpoiesz gravatar image dpoiesz  ( 2018-01-14 13:21:51 -0600 )edit

When you're getting this setup again it's a good idea to check the camera feed first to make sure it's working. Using rostopic echo to view the camera image info while viewing the images themselves in rviz is a good test to do.

PeteBlackerThe3rd gravatar image PeteBlackerThe3rd  ( 2018-01-15 04:42:29 -0600 )edit

I fixed a mapping mistake and now get the same error as this post:

I updated and upgraded my system during the troubleshooting process and accepted about 255 changes, i assume openCV3 was one of them

dpoiesz gravatar image dpoiesz  ( 2018-01-16 16:07:21 -0600 )edit

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Asked: 2018-01-13 15:19:10 -0600

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Last updated: Jan 14 '18