We are using Kinect in this robot for replicating the function of expensive laser range scanner. Kinect can deliver Point Cloud data which contains the depth of each point of surrounding. The Point Cloud data is processed and converted to data equivalent to a laser scanner using the ROS depthimage_to_laserscan package. The main function of this package is to slice a section of the Point Cloud data and convert it to a laser scan equivalent data type. The Pointcloud2 data type is sensor_msgs/PointCloud2 and for the laser scanner, the data type is sensor_msgs/LaserScan. This package will perform this processing and fake the laser scanner. The laser scanner output can be viewed using RViz. In order to run the conversion, we have to start the convertor nodelets that will perform this operation. We have to specify this in our launch file to start the conversion. The following is the required code in the launch file to start the depthimage_to_laserscan conversion:

  <!-- Fake laser -->
  <node pkg="nodelet" type="nodelet" name="laserscan_nodelet_manager" args="manager"/>
  <node pkg="nodelet" type="nodelet" name="depthimage_to_laserscan"
        args="load depthimage_to_laserscan/DepthImageToLaserScanNodelet laserscan_nodelet_manager">
    <param name="scan_height" value="10"/>
    <param name="output_frame_id" value="/camera_depth_frame"/>
    <param name="range_min" value="0.45"/>
    <remap from="image" to="/camera/depth/image_raw"/>
    <remap from="scan" to="/scan"/>
  </node>

Along with starting the nodelet, we need to set certain parameters of the nodelet for better conversion. Refer to http://wiki.ros.org/depthimage_to_laserscan for a detailed explanation of each parameter.

The laser scan of the preceding view is shown in the following screenshot. To view the laser scan, add the LaserScan option. This is similar to how we add the PointCloud2 option and change the Topic value of LaserScan to /scan: