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# pointcloud_to_laserscan parameter min_height

hey guys,

short question:

Is the pointcloud_to_laserscan package capable of using negative values as min_height?

Background information: I'm desperatly trying to get a scan out of my PointCloud2 data, that my kinect generates - as it happens the kinect is not on the ground level, which means that some obstacles have negative height values... that somehow seems to be a problem for the node - the obstacles are part of the pcl, but the laserscan does not see them... I hope you get what my problem is, for sure I can't be the first to try this :(

Edit: Update As a workaround I've changed some part of the cloud_to_scan.cpp file and manually increased the height - this works, even though I don't understand why -y+1 < min_height with min_height =0 works, wenn -y < min_height with a value of -1 fails...

I mean, if y is like 0.5 in the first case it is: -0.5+1 <0 => 0.5 < 0 => false in the second case: -0.5 < -1 => false

Edit:

Thanks for your answer, that indicates that somehow I messed up my package. I'm sure that I set the parameters correct in the launchfile, and just to check that I changed the default values - with no result.

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Yes, the min_height parameter can be negative (anything between -10.0 and 10.0 meters). The only thing to look out for is that pointcloud_to_laserscan assumes the input PointCloud to be in the Kinect optical frame (x to the right, y down, z forward), while most other coordinate systems in ROS have x forward, y to the left, z up. That means that -y is up in pointcloud_to_laserscan.

BTW, you can use the following command to adjust these parameters dynamically with a GUI; that makes parameter tuning much easier:

rosrun dynamic_reconfigure reconfigure_gui

more

hmm, I'm pretty sure my launchfile works and sets the parameters right(tried some few extrema, which led to the results I expected)...still negative values won't work :(

( 2012-10-10 16:42:19 -0500 )edit