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Why the SLAM have more than one maps in RVIZ? [closed]

asked 2011-05-17 13:56:06 -0600

gong gravatar image

updated 2014-01-28 17:09:41 -0600

ngrennan gravatar image

When I'm using gmapping to be SLAM in rviz, with the robot running there will generate more than one maps in RVIZ?

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Closed for the following reason the question is answered, right answer was accepted by mmwise
close date 2011-06-07 12:18:52

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Could you add the screenshot that you sent to the mailing list as well, since it helps to explain what you mean?
Eric Perko gravatar imageEric Perko ( 2011-05-17 14:51:01 -0600 )edit
How are you generating/publishing odometry (e.g. p2os or your own custom robot driver)? Is your odometry accurate? If you run the robot around with the fixed frame in rviz set to "/odom" and set the laser scan's "Decay time" to a large number, do you get a mostly consistent looking map?
Eric Perko gravatar imageEric Perko ( 2011-05-17 14:54:33 -0600 )edit
as you can see from the screenshot, the map is jumping from one place to another
gong gravatar imagegong ( 2011-05-17 20:08:24 -0600 )edit
I guess I wasn't clear about the "mostly consistent map". This would be without SLAM running, just using your odometry source to place the buffered laser scans into a mostly consistent reference frame.
Eric Perko gravatar imageEric Perko ( 2011-05-17 20:20:21 -0600 )edit
I set the fixed frames to "/odom" and set the laser scan's "delay time" to 10 seconds. It seems that I do not get the "mostly consistent map", because when the robot is running I cannot see the map in rviz until the robot is stoped.
gong gravatar imagegong ( 2011-05-17 20:55:55 -0600 )edit
Further more, I got an error message. Error: m_distanceThesholdCheck overridden!!! ... the odometry has a big jump here. this is probably a bug in the odometry/laser input. This error has been happened someday ago, I rewrite the odomety program to fix it. At that time, the formula was wrong.
gong gravatar imagegong ( 2011-05-17 21:00:43 -0600 )edit
Additional, I published odometry using the relative distance computed from odometry which provided by driver. The odmetry was like that : x = (current_odometry - last_odometry)*cos(theta), y = (current_odometry - last_odometry)*sin(theta), the theta was absolute value provided by gyro.
gong gravatar imagegong ( 2011-05-17 21:07:09 -0600 )edit

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answered 2011-05-24 01:49:18 -0600

gong gravatar image

I have been fix the problem. There is a mistake in my program about the odom computing. Thanks Eric and dornhege. Thank you so much!!

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answered 2011-05-18 00:21:09 -0600

dornhege gravatar image

Can you display the odom trajetory? It looks to me as you won't get something even near to the "mostly consistent map", but some jump in odometry.

Maybe it starts from some internal coordinates != 0, but send 0,0 as the first message?

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You are right. I think the problem is that I do not have a really fixed frame in the world coordinate. Though the fixed frame I set to /odom but it's not fixed. With the robot moving the location of /odom is change. Am I right?
gong gravatar imagegong ( 2011-05-18 13:48:06 -0600 )edit
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answered 2011-05-17 19:53:49 -0600

gong gravatar image

I have not enough Karma, so there is the link of the image. link text

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Hmm... the FAQ ( http://answers.ros.org/faq/ ) doesn't mention anything about needing a certain level of Karma to put an image into your post...
Eric Perko gravatar imageEric Perko ( 2011-05-17 20:22:04 -0600 )edit
I'm sorry, but it need Karma more than 20 to be able to put an image in the question.
gong gravatar imagegong ( 2011-05-17 21:01:28 -0600 )edit

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Asked: 2011-05-17 13:56:06 -0600

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Last updated: May 24 '11