Starting ROS Mono node

[ujur007]

I have some problem starting the Mono node from the SLAM2. when I do

rosrun ORB_SLAM2 Mono <path_to_vocabulary_file> <path_to_yaml_file>

it starts and loads the vocabulary but then the frame window remains empty and displays 'waiting for the images'. So whats the method to start Monocular node from topic /camera/image_raw?

[cecileclav]

Hi, you need to play a rosbag of the sequence you want to run the program on, in an other terminal window. It is fully explained on the README, at the end, but I copy the lines here :

Download a rosbag (e.g. V1_01_easy.bag) from the EuRoC dataset (http://projects.asl.ethz.ch/datasets/doku.php?id=kmavvisualinertialdatasets). Open 3 tabs on the terminal and run the following command at each tab:

roscore

rosrun ORB_SLAM2 Stereo Vocabulary/ORBvoc.txt Examples/Stereo/EuRoC.yaml true (that's what you already do, but you need to open a new terminal window and enter the following command line)

rosbag play --pause V1_01_easy.bag /cam0/image_raw:=/camera/left/image_raw /cam1/image_raw:=/camera/right/image_raw

Then, you just have to tap on the space tab to run the rosbag and ORB-SLAM2 will be provided with the images of the rosbag.

[ujur007]

@cecileclav Yes in case of sterio there was no problem running the node.. Actually in case of Mono when I run rosbag play --pause /home/orbslam/myownbag.bag /cam0/image_raw:=/camera/image_raw

I saw there was nothing!! Then I tried to publish images from topic camera/image_raw to record it using 'rosbag record topic' but that didnot work. I want to process my own data and for that I need to create .bag files.

[BW25]

ORBSLAM is subscribing to the Ros topic camera/image_raw, but nothing is being published there. So it is looking at nothing. We need to publish something to that topic.

This can be a .bag file, like with the stereo example. We can also use live input from a camera.

I used a usb webcam. There are a number of Ros nodes that can do this, I tried cv_camera. cv_camera publishes to a different topic, but we can remap it to publish to /camera/image_raw by adding this argument when running it: /cv_camera/image_raw:=/camera/image_raw

Full disclosure, I only just got this working myself, and ORBSLAM2 still isn't initializing, but hopefully this will help put you on the right track. In my case, the wired USB webcam can't be moved around much because of the length of the cable, making mapping a touch impractical.

[tnaderi]

Hi, I have the same issue. Where should I put "/cv_camera/image_raw:=/camera/image_raw" in which file? Thanks

[BW25]

See this link on remapping arguments in ROS. http://wiki.ros.org/Remapping%20Arguments

The remapping argument is given when you run cv_camera. Add it to the command you use to start the cv_camera node.

[tnaderi]

Thank you for your response. That is very clarifying. When I used calibration http://wiki.ros.org/camera_calibration the format of file is different from format of yaml file you have used in your orb_slam2 config folder. How can I convert the two format to each other. I tried to do that but the map is highly distorted. Is it possible that my calibration has problem?

[tnaderi]

Thank you