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output_frame on ar_track_alvar

asked 2014-04-14 08:20:13 -0600

Dipta gravatar image

Hello, I would like to test detecting AR Tag with ar_track_alvar launch using IndividualMarkersNoKinect with my IP Camera. Since I published my own image_raw topic and camera_info topic, I have no ideas where to put the output_frame for that ar_track package..

Can you guys help me?


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answered 2014-04-14 21:27:05 -0600

BennyRe gravatar image

The package documentation says

Output frame (string) -- The name of the frame that the published Cartesian locations of the AR tags will be relative to

So you should use the frame of the camera as output frame for alvar.

In my project I use

<arg name="output_frame" value="/camera" />

because my image gets published to

<param name="frame_id" type="string" value="camera" />

(I'm using the uvc_camera package for my cam.)

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answered 2014-06-05 21:08:03 -0600

Tanmay gravatar image

Sorry for the delayed response,

In addition to what BennyRe rightly said, I suggest you check your camera frame id with

rostopic echo /camera/camera_info    .

In this case, publishing with respect to the camera frame is a good idea, since ar_track_alvar returns marker coordinates. (It is similar to the ar_single and ar_multiple components of the ar_pose package. )

I had set my output_frame as v4l_frame using:

<param name="frame_id" value="/v4l_frame" />

in the corresponding launch file.

In case you do not have frame id being set (or your driver lacks camera_info as mine did), try including that in your driver (be it gscam / usb_cam / uvc_camera ).

In case your camera frame is not publish

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Asked: 2014-04-14 08:20:13 -0600

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Last updated: Jun 05 '14