Incorrect scanning frame with G4 model

[EwingKang]

The scanning frame, including the robot model is rotated by 180 degrees around Z axis. In this picture, the wall corner is actually on the right-front direction, while the arrow pointing at the LIDAR is at its left-hand-side

[EwingKang]

It turns out that there's a parameter called reversion, you have to set those manually.

<node name="ydlidar_node"  pkg="ydlidar"  type="ydlidar_node" output="screen">
    <param name="port"         type="string" value="/dev/ydlidar"/>  
    <param name="baudrate"     type="int"    value="115200"/>
    <param name="frame_id"     type="string" value="laser_frame"/>
    <param name="angle_fixed"  type="bool"   value="true"/>
    <param name="low_exposure"  type="bool"   value="false"/>
    <param name="heartbeat"    type="bool"   value="false"/>
    <param name="resolution_fixed"    type="bool"   value="true"/>
    <param name="reversion"    type="bool"   value="true"/>
    <param name="angle_min"    type="double" value="-180" />
    <param name="angle_max"    type="double" value="180" />
    <param name="range_min"    type="double" value="0.08" />
    <param name="range_max"    type="double" value="16.0" />
    <param name="ignore_array" type="string" value="" />
    <param name="samp_rate"    type="int"    value="9"/>
    <param name="frequency"    type="double" value="7"/>
  </node>

But still, the scanning direction is reversed compare to the standard definition of ROS (http://docs.ros.org/melodic/api/sensor_msgs/html/msg/LaserScan.html) which, which will cause problem if vehicle is moving.