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Map generated by Gmapping has bend on it

asked 2020-02-13 13:29:16 -0500

imanpakii gravatar image

Hello Every one,

I'm making the map with Gmapping in ROS but the problem I have is the map is not strait as it is in the real world. image description as you can see in the picture the rectangular shape has some orientation. it also in the picture below, the red box shows that the bedroom in the apartment has few degrees of orientation. what is the reason? I'm using Jackal with SICK LMS100 Lidar.

image description

any help would be appreciated Thank you Iman

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answered 2020-02-13 14:05:18 -0500

billy gravatar image

Two ways to improve this are by tuning your odometry and limit the speed while mapping.

Errors in the odom can be transferred into errors in the map so do your best to make sure that tuning for odom accurately captures encoder counts vs linear distance traveled (in each wheel) and difference in encoder counts while rotating. The tuning should be done on the surface where most error occurs or the surface that makes up most of the environment. If tuning on different surfaces results in a large difference in encoder_counts/distance (angle) then you would have to maybe aim for a middle spot and live with some error in the map. See the bit here about tuning odom http://wiki.ros.org/navigation/Tutori...

When you rotate the base while mapping, do so slowly to minimize wheel slip and minimize the lag the in lidar vs odom.

If straight walls appear curved in map it's mostly likely due to odometry tuning when moving straight, and if straight walls are straight in the map but a room is at angle to rest of map, it's likely caused by odom tuning when rotating or due to errors caused by rotating too quickly while mapping. Move slowly while mapping for best result.

Finally, if you really needed to, you could use photoshop to straighten out the map. If errors are small, navigation should work smoothly with a photoshop-straightened map.

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Thank you for your quick response. The first map above generated by the Gazebo environment. How can I tune odometry in Gazebo and simulator?

Thank you

imanpakii gravatar image imanpakii  ( 2020-02-13 14:38:34 -0500 )edit

Well tuning odom shouldn't be required if there is no error built into the simulation, but try mapping moving slowly.

billy gravatar image billy  ( 2020-02-13 15:24:30 -0500 )edit

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Asked: 2020-02-13 13:29:16 -0500

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Last updated: Feb 13 '20