ROS Answers: Open Source Q&A Forum - RSS feedhttps://answers.ros.org/questions/Open source question and answer forum written in Python and DjangoenROS Answers is licensed under Creative Commons Attribution 3.0Fri, 11 Oct 2019 09:53:13 -0500coordinate of velodyne datahttps://answers.ros.org/question/144071/coordinate-of-velodyne-data/hi there!i need help again......i just want to construct a height_map with velodyne data.Before defining the size of cells and the origin of coordinate in my grids,i think i have to know what coordinate does velodyne use to define the data it acquires.More specificly,which direction does the x axis point as well as y and z?And where is the coordinate origin?When i use rostopic echo command to find out the values of the velodyne points,i discover that all of them are positive and the minimum is zero (no negative values).Is that making sense?thank you.Tue, 25 Mar 2014 04:06:19 -0500https://answers.ros.org/question/144071/coordinate-of-velodyne-data/Comment by Lau for <p>hi there!i need help again......i just want to construct a height_map with velodyne data.Before defining the size of cells and the origin of coordinate in my grids,i think i have to know what coordinate does velodyne use to define the data it acquires.More specificly,which direction does the x axis point as well as y and z?And where is the coordinate origin?When i use rostopic echo command to find out the values of the velodyne points,i discover that all of them are positive and the minimum is zero (no negative values).Is that making sense?thank you.</p>
https://answers.ros.org/question/144071/coordinate-of-velodyne-data/?comment=188728#post-id-188728I have the same question . Have you solved it ?Sun, 03 Aug 2014 04:40:34 -0500https://answers.ros.org/question/144071/coordinate-of-velodyne-data/?comment=188728#post-id-188728Comment by jbinney for <p>hi there!i need help again......i just want to construct a height_map with velodyne data.Before defining the size of cells and the origin of coordinate in my grids,i think i have to know what coordinate does velodyne use to define the data it acquires.More specificly,which direction does the x axis point as well as y and z?And where is the coordinate origin?When i use rostopic echo command to find out the values of the velodyne points,i discover that all of them are positive and the minimum is zero (no negative values).Is that making sense?thank you.</p>
https://answers.ros.org/question/144071/coordinate-of-velodyne-data/?comment=144451#post-id-144451Have you tried looking at the pointclouds in rviz? Should help you figure out the coordinate system. To help, add a "Pose" display in the same frame_id as you see in the header of the velodyne messages.Tue, 25 Mar 2014 21:03:22 -0500https://answers.ros.org/question/144071/coordinate-of-velodyne-data/?comment=144451#post-id-144451Answer by chaoshydra for <p>hi there!i need help again......i just want to construct a height_map with velodyne data.Before defining the size of cells and the origin of coordinate in my grids,i think i have to know what coordinate does velodyne use to define the data it acquires.More specificly,which direction does the x axis point as well as y and z?And where is the coordinate origin?When i use rostopic echo command to find out the values of the velodyne points,i discover that all of them are positive and the minimum is zero (no negative values).Is that making sense?thank you.</p>
https://answers.ros.org/question/144071/coordinate-of-velodyne-data/?answer=335233#post-id-335233According to the answer [here](https://answers.ros.org/question/260542/difference-in-reference-frames-between-vlp-16-and-hdl-32-and-how-to-convert-them/), the coordinate system is listed as it states and I can confirm.
As for read velodyne data, echo the topic (I presume velodyne-points) is not going to help as it is showing the raw data. You can follow instruction on [here](https://answers.ros.org/question/202787/using-pointcloud2-data-getting-xy-points-in-python/) on converting raw data to readable array or just Rviz it. Fri, 11 Oct 2019 09:53:13 -0500https://answers.ros.org/question/144071/coordinate-of-velodyne-data/?answer=335233#post-id-335233