Ask Your Question
0

Does transforming from laser scan to point cloud change the order of the points?

asked 2018-02-14 04:19:28 -0600

Atik gravatar image

updated 2018-02-15 02:27:27 -0600

I am receiving laser scans with special information written into the intensity parameter.

When I convert the laser scans to point cloud using the high fidelity transformation does this change the number of points?

I use the special intensity for information regarding closeness to other items in the map in order to capture dynamic objects.

When I run the bag viewing the laser scans with the intensities in rviz it seems to work fine but when I convert it to point clouds and append the intensity it no longer fits leaving me to think that the high fidelity transformation may either use the intensity for something it shouldn't or simply change the number of points.

I hope I have provided enough information.

Can anyone shed some light on this?

ADD: I have tried using the other laser scan to point cloud transformation which yields the same results. My guess is that when the transform happens the cloud points are not in the same order as the laser scan points was in the beginning.

ADD: This however leads me to the question how I can then use my intensities with the point cloud when the order is different?

ADD: Maybe it could be that when I transform to base_frame that the points are put in a different order?

ADD: It seems that there is less points in the converted point cloud than there were in the laser scan ranges.

edit retag flag offensive close merge delete

Comments

What is the 'high fidelity' conversion node and what is the other one mentioned in the first add comment?

lucasw gravatar imagelucasw ( 2018-02-14 09:46:26 -0600 )edit

http://wiki.ros.org/laser_geometry , it is in the wiki...

Atik gravatar imageAtik ( 2018-02-15 02:26:02 -0600 )edit

You are probably losing points because the range is either below the minimum or above the maximum https://github.com/ros-perception/las... (is there not a standard laser scan to pointcloud node, everyone just has to call these library functions?)

lucasw gravatar imagelucasw ( 2018-02-15 11:38:27 -0600 )edit

But other than that the code looks like it preserves the order.

lucasw gravatar imagelucasw ( 2018-02-15 11:39:44 -0600 )edit
1

is there not a standard laser scan to pointcloud node, everyone just has to call these library functions?

@lucasw: laser_assembler.

gvdhoorn gravatar imagegvdhoorn ( 2018-02-15 11:55:02 -0600 )edit

1 Answer

Sort by ยป oldest newest most voted
0

answered 2018-02-15 03:45:35 -0600

Atik gravatar image

I found the way to use intensities after conversion to point cloud.

When you convert the point cloud the intensities get written into the channels array inside the point cloud object. Here intensities can he reached however in a normalized manner.

edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Question Tools

2 followers

Stats

Asked: 2018-02-14 04:19:28 -0600

Seen: 174 times

Last updated: Feb 15 '18