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laser_assembler cloud inaccuracy

asked 2013-11-01 15:56:22 -0600

pwong gravatar image

updated 2014-01-28 17:18:26 -0600

ngrennan gravatar image

I've tried to use the laser assembler to create a cloud, however the floors and the floor from the cloud isn't flat. Its more wavey than anything else.

The servo is moving at 110degs/sec and I'm using the periodic snapshotter to publish the pointcloud every second. I publish the transform of the servo and with the /scans, I send it to the laser_assembler.

I'm also unsure where to measure the servo rotation axis to the hokuyo utm-30lx, since I don't know exactly where the laser projects, it was a rough estimate.

What could be the main cause of the problem?

Thank you!

Edit1: Instead of it being wavey, after closer inspection the point cloud is seeing double, such that there is a zone where two table tops would be shown.

Edit2: The picture as a whole seems to look better as a whole if I don't overlap the scans over a period of time.

I'm going to make clouds of when the laser scan makes one sweep from top to bottom and a sweep going from bottom to top.

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answered 2013-11-19 19:55:26 -0600

My first guess would be that you´re a timestamping problem. If the timestamps of your joint angle sensor data and your LIDAR scan have an offset, this would explain you seeing that double table top. What you could do is add a timestamp offset to the joint_states or tf you publish and play adjust it till you only see a single table top in the assembler.

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Thank you for the answer! I see that in the laser scanner node, it takes in a time offset as a parameter, so that would be really easily to adjust. Would the method to add the offset manually just by literally adding(or subtracting) time from my header.stamp?

pwong gravatar image pwong  ( 2013-11-21 05:19:29 -0600 )edit

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Asked: 2013-11-01 15:56:22 -0600

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Last updated: Nov 19 '13