Interpreting stored cloud file from PointCloud2 data type

asked 2012-01-31 23:31:43 -0500

alfa_80
1051 ●123 ●137 ●150

updated 2012-02-01 00:08:13 -0500

I am having a problem in interpreting a point cloud data stored in PointCloud2 of data type. The file is generated by "rostopic echo.." my cloud topic. My goal is to find corresponding x, y and z values, in terms of coordinates so that I can use them in plotting with MatLab or Octave. I am aware of this link, but, I still cannot see the use of it.

The fields in the stored file looks like this:

%time,field.header.seq,field.header.stamp,field.header.frame_id,field.height,field.width,field.fields0.name,field.fields0.offset,field.fields0.datatype,field.fields0.count,field.fields1.name,field.fields1.offset "and so on"

Or, is it wise to convert from PointCloud2 first into another format before I can plot it. If so, in what format, it serves the best for this purpose? Or any other smarter way of doing it.

Thanks in advance.

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answered 2012-07-11 05:54:09 -0500

tbernhard

80 ●3 ●6 ●12

updated 2012-07-11 08:27:30 -0500

There is probably a more direct method, but I've used PCL's .pcd format to accomplish this.

EDIT: Dan Lazewatsky pointed out pointcloud_to_pcd, which converts a ROS PointCloud2 msg to a .pcd file. See his comment for the docs.

Once you have it as a .pcd, it should be fairly easy to parse. After the header the points are listed one per line: x y z rgb. Note that PCL packs the RBG (and alpha, if you're using it) channels into a single float.

Related docs and tutorials: pcl::fromROSmsg | writing to a .pcd file | .pcd file format