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Error of a map made by gmapping

asked 2018-07-24 21:53:59 -0500

taka gravatar image

I'm trying to run a waffle pi along a path of 60cm width. During the test, I noticed that there is difference between a map made by gmapping and local map made during navigation.

Please see the attached image or link. Black line is made by gmapping and green dotted line is made during navigation. These lines are misaligned and the difference is approximately 20cm.

This phenomenon still happens after update of a Turtlebot3 package (v1.0.0) and a OpenCR firmware (v1.2.0).

Please give me your comment and/or advise.


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I don't see any error in mapping. I see an offset in localization. Are you running any nodes to locate the robot in the map like AMCL?

billy gravatar image billy  ( 2018-07-24 23:30:56 -0500 )edit

Thanks. There is an offset between a map made by gmapping and local map made during navigation. I think this offset has a bad influence for navigation. I'm not sure why the offset occurs and how to minimize the offset. I use AMCL particles for localization. Thank you in advance.

taka gravatar image taka  ( 2018-07-25 05:14:50 -0500 )edit

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answered 2018-07-25 04:17:27 -0500

This seams like error in odometry data or that you are running a robot without localization. Try to run AMCL node for localization. See here.

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Thanks. As shown in rqt, I run the AMCL node during navigation. As you say, there may be error in odometory data, but I don't know how I can fix it.

taka gravatar image taka  ( 2018-07-25 18:28:05 -0500 )edit

I think there is a problem during map making. I noticed two things.

(1) When location of robot changes, results of laser scan (green dot in rviz) points to different position. Please compare red circle in image1 and image2.

taka gravatar image taka  ( 2018-07-25 19:20:34 -0500 )edit

(2) While the robot slowly goes forward during map making, it looks like that the robot goes back and forth in rviz. Please see video. I think this is related to (1).

Thanks in advance.

taka gravatar image taka  ( 2018-07-25 19:30:33 -0500 )edit

this is all OK. The robot "jumps" when slam calculates data. It seams that your odometry data says that robot moves slower than it really moves. Please check your odometry data, this should be in some yaml file of your diff drive controller. It could be that your wheels are too small...

destogl gravatar image destogl  ( 2018-07-26 01:22:58 -0500 )edit

Also you can change the covarinance of your odometry. I am just not sure where, It should be published by your differential controller or it is defined in configuations of your slam/localization.

destogl gravatar image destogl  ( 2018-07-26 01:24:54 -0500 )edit

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Asked: 2018-07-24 21:53:59 -0500

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Last updated: Jul 25 '18