# skewed map gmapping

Hello,

For the past few weeks I have been trying to build a map of our laboratory using slam_gmapping. I am operating a Powerbot via the RosAria package. It has a SICK laser range finder which I am driving using the sicktoolbox_wrapper package. I have set up my transform tree by following this link. Everything seems to work fine and I got this map (please zoom in a little bit). This is the map of our laboratory. The actual lab is basically rectangular-shaped with a rectangular line of desks in the middle. On either side of this 'island' of desks, there are two open spaces that are strictly parallel to each other. In fact, the desks in the middle should form a perfect rectangle. As can be seen from the map produced, the desks are skewed and opposite walls of the lab are not parallel.

I am running the following running command to set the parameters of gmapping

rosrun gmapping slam_gmapping scan:=scan _minimumScore:=50.0 _map_update_interval:=2.0 _linearUpdate:=0.05 _angularUpdate:=0.01


Can anyone help me identify what's wrong? Does this have to do with bad odometry? How would I check? My tf tree is: map --> odom --> base_link --> laser.

EDIT:

I have noticed that this happens when after a short while of starting the gmapping node, if the robot encounters a bend in the environment (around 0.75m after starting), the end resulting map will be skewed. This was not the case when I moved the robot along a straight line for, say, 2 metres and then turned around the bend. Can anyone explain why this happens please?

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